Photo-detecting apparatus with low dark current

ABSTRACT

A photo-detecting apparatus is provided. The photo-detecting apparatus includes a carrier conducting layer having a first surface; an absorption region is doped with a first dopant having a first conductivity type and a first peak doping concentration, wherein the carrier conducting layer is doped with a second dopant having a second conductivity type and a second peak doping concentration, wherein the carrier conducting layer comprises a material different from a material of the absorption region, wherein the carrier conducting layer is in contact with the absorption region to form at least one heterointerface, wherein a ratio between the first peak doping concentration of the absorption region and the second peak doping concentration of the carrier conducting layer is equal to or greater than 10; and a first electrode and a second electrode both formed over the first surface of the carrier conducting layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This present application is a continuation-in-part of and claimspriority to U.S. patent application Ser. No. 17/005,288, having a filingdate of Aug. 27, 2020, which claims the benefit of U.S. ProvisionalPatent Application No. 62/892,551, having a filing date of Aug. 28,2019, U.S. Provisional Patent Application No. 62/899,153, having afiling date of Sep. 12, 2019, U.S. Provisional Patent Application No.62/929,089, having a filing date of Oct. 31, 2019, and U.S. ProvisionalPatent Application No. 63/053,723, having a filing date of Jul. 20,2020, each of which is incorporated by reference herein in its entirety.The present application claims filing benefit of U.S. Provisional PatentApplication No. 63/192,105, having a filing date of May 24, 2021, U.S.Provisional Patent Application No. 63/223,056, having a filing date ofJul. 18, 2021, and U.S. Provisional Patent Application No. 63/226,761,having a filing date of Jul. 29, 2021, each of which is incorporated byreference herein in its entirety.

BACKGROUND

Photodetectors may be used to detect optical signals and convert theoptical signals to electrical signals that may be further processed byanother circuitry. Photodetectors may be used in consumer electronicsproducts, image sensors, high-speed optical receiver, datacommunications, direct/indirect time-of-flight (TOF) ranging or imagingsensors, medical devices, and many other suitable applications.

SUMMARY

The present disclosure relates generally to a photo-detecting apparatusand an image system including the same.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes an absorption region including a first dopant having a firstpeak doping concentration; and a substrate supporting the absorptionregion, where the substrate includes a second dopant having a secondpeak doping concentration lower than the first peak dopingconcentration; where the absorption region includes a material differentfrom a material of the substrate.

According to an embodiment of the present disclosure, a photo-detectingapparatus is provided. The photo-detecting apparatus, includes aphoto-detecting device including: a carrier conducting layer having afirst surface and a second surface; an absorption region in contact withthe carrier conducting layer and configured to receive an optical signaland to generate photo-carriers in response to the optical signal,wherein the absorption region is doped with a first dopant having afirst conductivity type and a first peak doping concentration, whereinthe carrier conducting layer is doped with a second dopant having asecond conductivity type and a second peak doping concentration, whereinthe carrier conducting layer includes a material different from amaterial of the absorption region, wherein the carrier conducting layeris in contact with the absorption region to form at least oneheterointerface, wherein a ratio between a doping concentration of theabsorption region and a doping concentration of the carrier conductingregion at the at least one heterointerface is equal to or greater than10; and a first electrode and a second electrode formed over a same sideof the carrier conducting layer.

According to an embodiment of the present disclosure, a photo-detectingapparatus is provided. The photo-detecting apparatus, includes aphoto-detecting device including: a carrier conducting layer having afirst surface and a second surface; an absorption region in contact withthe carrier conducting layer and configured to receive an optical signaland to generate photo-carriers in response to the optical signal,wherein the absorption region is doped with a first dopant having afirst conductivity type and a first peak doping concentration, whereinthe carrier conducting layer is doped with a second dopant having asecond conductivity type and a second peak doping concentration, whereinthe carrier conducting layer includes a material different from amaterial of the absorption region, wherein the carrier conducting layeris in contact with the absorption region to form at least oneheterointerface, wherein a ratio between a doping concentration of theabsorption region and a doping concentration of the carrier conductingregion at the at least one heterointerface is equal to or greater than10 or a ratio between the first peak doping concentration of theabsorption region and the second peak doping concentration of thecarrier conducting region is equal to or greater than 10; and a seconddoped region in the carrier conducting layer and in contact with theabsorption region, wherein the second doped region is doped with afourth dopant having a conductivity type the same as the firstconductivity type and having a fourth peak doping concentration higherthan the first peak doping concentration.

According to an embodiment of the present disclosure, a photo-detectingapparatus is provided. The photo-detecting apparatus, includes aphoto-detecting device including: a carrier conducting layer having afirst surface and a second surface; an absorption region in contact withthe carrier conducting layer and configured to receive an optical signaland to generate photo-carriers in response to the optical signal,wherein the absorption region is doped with a first dopant having afirst conductivity type and a first peak doping concentration, whereinthe carrier conducting layer is doped with a second dopant having asecond conductivity type and a second peak doping concentration, whereinthe carrier conducting layer includes a material different from amaterial of the absorption region, wherein the carrier conducting layeris in contact with the absorption region to form at least oneheterointerface, wherein a ratio between a doping concentration of theabsorption region and a doping concentration of the carrier conductingregion at the at least one heterointerface is equal to or greater than10, a ratio between the first peak doping concentration of theabsorption region and the second peak doping concentration of thecarrier conducting region is equal to or greater than 10 and at least50% of the absorption region is doped with a doping concentration of thefirst dopant equal to or greater than 1×10¹⁶ cm³.

According to an embodiment of the present disclosure, a photo-detectingapparatus is provided. The photo-detecting apparatus, includes aphoto-detecting device including: a carrier conducting layer having afirst surface and a second surface; an absorption region in contact withthe carrier conducting layer and configured to receive an optical signaland to generate photo-carriers in response to the optical signal,wherein the absorption region is doped with a first dopant having afirst conductivity type and a first peak doping concentration, whereinthe carrier conducting layer is doped with a second dopant having asecond conductivity type and a second peak doping concentration, whereinthe carrier conducting layer includes a material different from amaterial of the absorption region, wherein the carrier conducting layeris in contact with the absorption region to form at least oneheterointerface, wherein a ratio between the first peak dopingconcentration of the absorption region and the second peak dopingconcentration of the carrier conducting region is equal to or greaterthan 10; and a first electrode formed over the first surface of thecarrier conducting layer and electrically coupled to the carrierconducting layer, wherein the first electrode is separated from theabsorption region, wherein the first electrode is configured to collecta portion of the photo-carriers; and a second electrode formed over thefirst surface of the carrier conducting layer and electrically coupledto the absorption region.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatus,includes a photo-detecting device including: a substrate having a firstsurface and a second surface; an absorption region over a first surfaceof the substrate and configured to receive an optical signal and togenerate photo-carriers in response to the optical signal, wherein theabsorption region is doped with a first dopant having a firstconductivity type and a first peak doping concentration, wherein thesubstrate is doped with a second dopant having a second conductivitytype and a second peak doping concentration, wherein the substrateincludes a material different from a material of the absorption region,wherein the substrate is in contact with the absorption region to format least one heterointerface, wherein a ratio between the first peakdoping concentration of the absorption region and the second peak dopingconcentration of the substrate is equal to or greater than 10 or a ratiobetween a doping concentration of the absorption region and a dopingconcentration of the substrate at the at least one heterointerface isequal to or greater than 10; and a first electrode formed over the firstsurface of the substrate and electrically coupled to the substrate,wherein the first electrode is separated from the absorption region,wherein the first electrode is configured to collect a portion of thephoto-carriers; and a second electrode formed over the first surface ofthe substrate and electrically coupled to the absorption region.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatus,includes a photo-detecting device including: an absorption regionconfigured to receive an optical signal and to generate photo-carriersin response to the optical signal, wherein the absorption region isdoped with a first dopant having a first conductivity type and a firstpeak doping concentration; a passivation layer over the absorptionregion and having a first surface and a second surface opposite to thefirst surface; wherein the passivation layer is doped with a seconddopant having a second conductivity type and a second peak dopingconcentration, wherein the passivation layer includes a materialdifferent from a material of the absorption region, wherein thepassivation layer is in contact with the absorption region to form atleast one heterointerface, wherein a ratio between the first peak dopingconcentration of the absorption region and the second peak dopingconcentration of the passivation layer is equal to or greater than 10 ora ratio between a doping concentration of the absorption region and adoping concentration of the passivation layer at the at least oneheterointerface is equal to or greater than 10; and a first electrodeformed over the first surface of the passivation layer and electricallycoupled to the passivation layer, wherein the first electrode isseparated from the absorption region, wherein the first electrode isconfigured to collect a portion of the photo-carriers; and a secondelectrode formed over the first surface of the passivation layer andelectrically coupled to the absorption region.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes a photo-detecting device including: a carrier conducting layerhaving a first surface and a second surface; an absorption region incontact with the carrier conducting layer and configured to receive anoptical signal and to generate photo-carriers in response to the opticalsignal, wherein the absorption region is doped with a first dopanthaving a first conductivity type and a first peak doping concentration,wherein the carrier conducting layer is doped with a second dopanthaving a second conductivity type and a second peak dopingconcentration, wherein the carrier conducting layer includes a materialdifferent from a material of the absorption region, wherein the carrierconducting layer is in contact with the absorption region to form atleast one heterointerface, wherein a ratio between a dopingconcentration of the absorption region and a doping concentration of thecarrier conducting layer at the at least one heterointerface is equal toor greater than 10 or a ratio between the first peak dopingconcentration of the absorption region and the second peak dopingconcentration of the carrier conducting layer is equal to or greaterthan 10; and one or more switches electrically coupled to the absorptionregion and partially formed in the carrier conducting layer, whereineach of the one or more switches includes a control electrode and areadout electrode that are formed over the first surface and areseparated from the absorption region; and an electrode formed over thefirst surface, and the electrode electrically coupled to the absorptionregion.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes a photo-detecting device including: a carrier conducting layerhaving a first surface and a second surface; an absorption region incontact with the carrier conducting layer and configured to receive anoptical signal and to generate photo-carriers in response to the opticalsignal, wherein the absorption region is doped with a first dopanthaving a first conductivity type and a first peak doping concentration,wherein the carrier conducting layer is doped with a second dopanthaving a second conductivity type and a second peak dopingconcentration, wherein the carrier conducting layer includes a materialdifferent from a material of the absorption region, wherein the carrierconducting layer is in contact with the absorption region to form atleast one heterointerface, wherein a ratio between a dopingconcentration of the absorption region and a doping concentration of thecarrier conducting layer at the at least one heterointerface is equal toor greater than 10 or a ratio between the first peak dopingconcentration of the absorption region and the second peak dopingconcentration of the carrier conducting layer is equal to or greaterthan 10; and one or more switches electrically coupled to the absorptionregion and partially formed in the carrier conducting layer, whereineach of the one or more switches includes a control electrode and areadout electrode that are formed a same side of the carrier conductinglayer; a second doped region in the carrier conducting layer and incontact with the absorption region, wherein the second doped region isdoped with a fourth dopant having a conductivity type the same as thefirst conductivity type and having a fourth peak doping concentrationhigher than the first peak doping concentration; and an electrodeelectrically coupled to the second doped region.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes a photo-detecting device including: a carrier conducting layerhaving a first surface and a second surface; an absorption region incontact with the carrier conducting layer and configured to receive anoptical signal and to generate photo-carriers in response to the opticalsignal, wherein the absorption region is doped with a first dopanthaving a first conductivity type and a first peak doping concentration,wherein the carrier conducting layer is doped with a second dopanthaving a second conductivity type and a second peak dopingconcentration, wherein the carrier conducting layer includes a materialdifferent from a material of the absorption region, wherein the carrierconducting layer is in contact with the absorption region to form atleast one heterointerface, wherein a ratio between a dopingconcentration of the absorption region and a doping concentration of thecarrier conducting layer at the at least one heterointerface is equal toor greater than 10 or a ratio between the first peak dopingconcentration of the absorption region and the second peak dopingconcentration of the carrier conducting layer is equal to or greaterthan 10; and one or more switches electrically coupled to the absorptionregion and partially formed in the carrier conducting layer. Thephoto-detecting apparatus further includes one or more readout circuitselectrically to the respective switch, and the one or more readoutcircuits includes a voltage-control transistor between a transfertransistor and a capacitor.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes an absorption region doped with a conductivity type andincludes a first dopant having a first peak doping concentration; acarrier conducting layer in contact with the absorption region, whereinthe carrier conducting layer includes a conducting region doped with aconductivity type and including a second dopant having a second peakdoping concentration lower than the first peak doping concentration,wherein the carrier conducting layer includes or is composed of amaterial different from a material of the absorption region, and whereinthe conducting region has a depth less than 5 μm.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes an absorption region doped with a first dopant having a firstpeak doping concentration; a first contact region having a conductivitytype; a second contact region having a conductivity type different fromthe conductivity type of the first contact region; a charge regionhaving a conductivity type the same as the conductivity type of thesecond contact region, where a part of the charge region is between thefirst contact region and the second contact region; a substratesupporting the absorption region, and the substrate includes a seconddopant having a second peak doping concentration lower than the firstpeak doping concentration; where the absorption region includes amaterial different from a material of the substrate.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes a substrate; an absorption region supported by the substrateand doped with a first dopant having a first conductivity type; multiplefirst contact regions each having a conductivity type different from thefirst conductivity type and formed in the substrate; a second dopedregion formed in the absorption region and having a conductivity typethe same as the first conductivity type; and multiple third contactregions each having a conductivity type the same as the firstconductivity type and formed in the substrate; wherein the first contactregions are arranged along a first plane, and the third contact regionsare arranged along a second plane different form the first plane. Insome embodiments, multiple multiplication regions are formed between themultiple third contact regions and multiple first contact regions.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes an absorption region; a first contact region having aconductivity type; a second contact region in the absorption region andhaving a conductivity type different from the conductivity type of thefirst contact region; a charge region having a conductivity type thesame as the conductivity type of the second contact region, where thecharge region is closer to the second contact region than the firstcontact region is; a substrate supporting the absorption region, whereinthe charge region and the first contact region are formed in thesubstrate. The photo-detecting apparatus further includes a modificationelement integrated with the substrate for modifying a position wheremultiplication occurs in the substrate.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes a substrate; an absorption region supported by the substrate; afirst contact region having a conductivity type formed in the substrate;a second contact region formed in the absorption region and having aconductivity type different from the conductivity type of the firstcontact region; a charge region formed in the substrate and having aconductivity type the same as the conductivity type of the secondcontact region; wherein a depth of the charge region is less than adepth of the first contact region. In some embodiments, the depth of thecharge region is between the depth of the second contact region and thedepth of the first contact region.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes a photo-detecting device including: a substrate having a firstsurface and a second surface; an absorption region over a first surfaceof the substrate and configured to receive an optical signal and togenerate photo-carriers in response to the optical signal, wherein theabsorption region is doped with a first dopant having a firstconductivity type and a first peak doping concentration, wherein thesubstrate is doped with a second dopant having a second conductivitytype and a second peak doping concentration, wherein the substrateincludes a material different from a material of the absorption region,wherein the substrate is in contact with the absorption region to format least one heterointerface, wherein a ratio between a dopingconcentration of the absorption region and a doping concentration of thesubstrate at the at least one heterointerface is equal to or greaterthan 10 or a ratio between the first peak doping concentration of theabsorption region and the second peak doping concentration of thesubstrate is equal to or greater than 10; wherein the substrate furtherincludes a waveguide configured to guide and confine the optical signalpropagating through a defined region of the substrate to couple theoptical signal to the absorption region.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes a photo-detecting device including: a carrier conducting layerhaving a first surface and a second surface; an absorption region incontact with the carrier conducting layer and configured to receive anoptical signal and to generate photo-carriers in response to the opticalsignal, wherein the absorption region is doped with a first dopanthaving a first conductivity type and a first peak doping concentration,wherein the carrier conducting layer is doped with a second dopanthaving a second conductivity type and a second peak dopingconcentration, wherein the carrier conducting layer includes a materialdifferent from a material of the absorption region, wherein the carrierconducting layer is in contact with the absorption region to form atleast one heterointerface, wherein a ratio between a dopingconcentration of the absorption region and a doping concentration of thecarrier conducting layer at the at least one heterointerface is equal toor greater than 10; and N switches electrically coupled to theabsorption region and partially formed in the carrier conducting layer.The photo-detecting apparatus further includes Y control signalsdifferent from each other and electrically coupled to thephoto-detecting device, wherein Y≤N and Y is a positive integer. Each ofthe control signal controls one or more of the switches of thephoto-detecting device.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes an absorption region including a first dopant having a firstpeak doping concentration; and a substrate supporting the absorptionregion, where the substrate includes a second dopant having a secondpeak doping concentration lower than the first peak dopingconcentration, where the absorption region includes a material having abandgap less than a bandgap of a material of the substrate, where abuilt-in electrical field region is across an interface between thesubstrate and the absorption region, where a first width of the built-inelectrical field region in the substrate is greater than a second widthof the built-in electrical field region in the absorption region so thatthe dark current is generated mostly from the substrate.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes an absorption region configured to receive an optical signaland generate photo-carriers having a first polarity and a secondpolarity; a lightly-doped region configured to receive a portion of thephoto-carriers having the first polarity from the absorption region; anda gain component configured to receive a portion of the photo-carriershaving the first polarity from the lightly-doped region and to generatean electrical signal having the second polarity, where a number of theelectrical charges of the electrical signal having the second polaritygenerated by the gain component is greater than a number of electricalcharges of the photo-carriers generated by the absorption region.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes an absorption region that is doped with a first dopant typehaving a first peak doping concentration, the absorption regionconfigured to receive an optical signal and generate photo-carriershaving a first polarity and a second polarity; a lightly-doped regionthat is doped with a second dopant type having a second peak dopingconcentration, the lightly-doped region configured to receive a portionof the photo-carriers having the first polarity from the absorptionregion, where the first dopant type is different from the second dopanttype; and a gain component configured to receive a portion of thephoto-carriers having the first polarity from the lightly-doped regionand to generate an electrical signal having the second polarity, where aratio of the first peak doping concentration of the absorption region tothe second peak doping concentration of the lightly-doped region isequal to or greater than 10, and where a number of the electricalcharges of the electrical signal having the second polarity generated bythe gain component is greater than a number of electrical charges of thephoto-carriers generated by the absorption region.

According to another embodiment of the present disclosure, a method foramplifying photo-carriers received by a photo-detecting apparatus havinga gain component is provided. The method including: receiving anoptical-signal in an absorption region to generate photo-carriers havinga first and a second type; steering the first type of photo-carriers toa gain region; and generating an amplified electrical signal having thesecond type, where generating the amplified electrical signal includes:applying a first voltage to an emitter electrode of the gain component;applying a second voltage to a collector electrode of the gaincomponent, such that a forward-bias is created across a p-n junctionbetween an emitter region of the gain component and a lightly-dopedregion of the gain component, and that a reverse-bias is created acrossthe p-n junction between a collector region of the gain component andthe lightly-doped region of the gain component; receiving a first typeof carriers in the lightly-doped region of the gain component toincrease the forward-bias between the emitter region and thelightly-doped region; and collecting a second type of carriers emittedfrom the emitter region by the collector region as an amplifiedelectrical signal.

According to another embodiment of the present disclosure, aphoto-detecting apparatus is provided. The photo-detecting apparatusincludes an absorption region configured to receive an optical signaland generate photo-carriers having a first polarity and a secondpolarity; a substrate configured to receive a portion of thephoto-carriers having the first polarity from the absorption region; andone or more switches electrically coupled to the absorption region andat least partially formed in the substrate, wherein each of the switchesincludes a gain component configured to receive a portion of thephoto-carriers having the first polarity and to generate an electricalsignal having the second polarity, where a number of the electricalcharges of the electrical signal having the second polarity generated bythe gain component is greater than a number of electrical charges of thephoto-carriers generated by the absorption region.

According to an embodiment of the present disclosure, an imaging systemis provided. The imaging system includes a transmitter unit capable ofemitting light, and a receiver unit including an image sensor includingthe photo-detecting apparatus.

Another example aspect of the present disclosure is directed to anoptical sensing apparatus that includes a substrate; one or more pixelssupported by the substrate, where each of the pixel comprises anabsorption region supported by the substrate, and where the absorptionregion configured to receive an optical signal and generatephoto-carriers in response to receiving the optical signal; one or morelenses over the respective pixel of the one or more pixels, where theone or more lenses are composed of a first material having a firstrefractive index; and an encapsulation layer over the one or more lensesand composed of a second material having a second refractive indexbetween 1.3 to 1.8, where a difference between the first refractiveindex and the second refractive index is above an index threshold suchthat a difference between an effective focal length of the one or morelenses and a distance between the one or more lenses and the one or morepixels is within a distance threshold.

In some implementations, the first refractive index of the one or morelenses is not less than 3, where the difference between the firstrefractive index and the second refractive index of the encapsulationlayer is not less than 0.5.

In some implementations, the optical sensing apparatus can include afirst planarization layer between the encapsulation layer and the one ormore lenses, where the first planarization layer is composed of a thirdmaterial having a third refractive index that is within a threshold fromthe second refractive index.

In some implementations, the optical sensing apparatus can include afirst anti-reflection layer between the one or more lenses and the firstplanarization layer, where the first anti-reflection layer is composedof a fourth material having a fourth refractive index between the thirdrefractive index of the first planarization layer and the firstrefractive index of the one or more lenses.

In some implementations, the optical sensing apparatus can include afilter layer between the first planarization layer and the encapsulationlayer, where the filter layer is configured to pass optical signalhaving a specific wavelength range.

In some implementations, the optical sensing apparatus can include asecond planarization layer between the one or more lenses and thesubstrate.

In some implementations, the first planarization layer or the secondplanarization layer is composed of a material comprising polymer havinga refractive index between 1 and 2.

In some implementations, the optical sensing apparatus can include asecond anti-reflection layer between the first planarization layer andthe encapsulation layer, where the second anti-reflection layer iscomposed of a sixth material having a sixth refractive index between thesecond refractive index of the encapsulation layer and the thirdrefractive index of the first planarization layer.

In some implementations, the optical sensing apparatus can include afilter layer between the one or more lenses and the one or more pixels,where the filter layer is configured to pass optical signal having aspecific wavelength range.

In some implementations, the optical sensing apparatus can include asecond planarization layer between the filter layer and the substrate.

In some implementations, the optical sensing apparatus can include acarrier substrate and an integrated circuit layer between the one ormore pixels and the carrier substrate, where the integrated circuitlayer includes a control circuit configured to control the one or morepixels.

In some implementations, the substrate is composed of a materialcomprising silicon. In some implementations, the absorption region iscomposed of a material comprising germanium.

Another example aspect of the present disclosure is directed to anoptical sensing apparatus that includes a substrate; one or more pixelssupported by the substrate, where each of the pixel comprises anabsorption region supported by the substrate, and where the absorptionregion is configured to receive an optical signal and generatephoto-carriers in response to receiving the optical signal; one or morelenses over the respective pixel of the one or more pixels, where theone or more lenses are composed of a first material having a firstrefractive index; an encapsulation layer over the one or more lenses andcomposed of a second material having a second refractive index lowerthan the first refractive index; and a first planarization layer betweenthe encapsulation layer and the one or more lenses and composed of athird material having a third refractive index that is within athreshold from the second refractive index.

In some implementations, the optical sensing apparatus can furtherinclude a first anti-reflection layer between the one or more lenses andthe encapsulation layer, where the first anti-reflection layer iscomposed of a fourth material having a fourth refractive index betweenthe third refractive index of the first planarization layer and thefirst refractive index of the one or more lenses.

In some implementations, the optical sensing apparatus can furtherinclude a filter layer between the first planarization layer and theencapsulation layer, where the filter layer is configured to passoptical signal having a specific wavelength range.

In some implementations, the optical sensing apparatus can furtherinclude a second planarization layer between the one or more lenses andthe substrate. In some implementations, the first planarization layer orthe second planarization layer is composed of a material comprisingpolymer having a refractive index between 1 and 2.

In some implementations, the optical sensing apparatus can furtherinclude a second anti-reflection layer between the first planarizationlayer and the encapsulation layer, where the second anti-reflectionlayer is composed of a sixth material having a sixth refractive indexbetween the second refractive index of the encapsulation layer and thethird refractive index of the first planarization layer.

In some implementations, the optical sensing apparatus can furtherinclude a filter layer between the one or more lenses and the one ormore pixels, where the filter layer is configured to pass optical signalhaving a specific wavelength range.

In some implementations, the optical sensing apparatus can furtherinclude a second planarization layer between the filter layer and thesubstrate.

In some implementations, the optical sensing apparatus can furtherinclude a carrier substrate and an integrated circuit layer between theone or more pixels and the carrier substrate, where the integratedcircuit layer comprises a control circuit configured to control the oneor more pixels.

In some implementations, the first refractive index of the one or morelenses is not less than 3. In some implementations, a difference betweenthe first refractive index of the one or more lenses and the secondrefractive index of the encapsulation layer is not less than 0.5. Insome implementations, a difference between the third refractive index ofthe first planarization layer and the first refractive index of the oneor more lenses is not less than 0.5.

In some implementations, the absorption regions of the one or morepixels are at least partially embedded in a substrate. In someimplementations, the one or more pixels are multiple pixels arranged inone-dimensional and two-dimensional.

Another example aspect of the present disclosure is directed to anoptical sensing apparatus that includes a substrate; one or more pixelssupported by the substrate, where each of the pixel comprises anabsorption region supported by the substrate, and where the absorptionregion is configured to receive an optical signal and generatephoto-carriers in response to receiving the optical signal; one or morelenses over the respective pixel of the one or more pixels, where theone or more lenses are composed of a first material having a firstrefractive index; a first planarization layer over the one or morelenses and composed of a second material having a second refractiveindex, where a difference between the second refractive index and thefirst refractive index is not less than 0.5.

Another example aspect of the present disclosure is directed to anoptical sensing apparatus that includes a substrate; one or more pixelssupported by the substrate, where each of the pixel comprises anabsorption region supported by the substrate, and where the absorptionregion is configured to receive an optical signal and generatephoto-carriers in response to receiving the optical signal; one or morelenses over the respective pixel of the one or more pixels, where theone or more lenses are composed of a first material having a firstrefractive index; a layer directly formed over the one or more lensesand composed of a second material having a second refractive index,where a difference between the second refractive index and the firstrefractive index is not less than 0.5.

Another example aspect of the present disclosure is directed to anoptical sensing apparatus that includes a photodetector. Thephotodetector includes a first substrate comprising a first material; anabsorption region formed on or at least partially in the firstsubstrate, where the absorption region comprises a second material, andwhere the absorption region is configured to receive an optical signaland to generate a photo-current in response to receiving the opticalsignal; a second substrate bonded to the first substrate, where thesecond substrate comprises the first material; and first circuitryformed in the second substrate, where the first circuitry is configuredto convert the photo-current and to an analog voltage output forprocessing; and a third substrate coupled to the photodetector, wherethe third substrate comprising second circuitry configured to processthe analog voltage output to generate a digital output.

In some implementations, the absorption region comprises an array ofpixels. In some implementations, the array of pixels are electricallycoupled together to generate the photo-current. In some implementations,the first material comprises silicon, and wherein the second materialcomprises germanium.

In some implementations, the optical sensing apparatus can include alens array configured to focus the optical signal to the array ofpixels.

In some implementations, the first circuitry comprises a low-noisepreamplifier configured to convert the photo-current and to a voltageoutput. In some implementations, the first circuitry further comprisesan amplifier configured to amplify the voltage output. In someimplementations, the second circuitry further comprises ananalog-to-digital converter configured to convert the amplified voltageoutput to a digital signal. In some implementations, the secondcircuitry further comprises a micro-controller configured to process thedigital signal.

In some implementations, the second substrate is bonded to the thirdsubstrate, the second substrate is arranged between the first substrateand the third substrate, and the first substrate is arranged to receivethe optical signal. In some implementations, the third substrate iswire-bonded to the first substrate or the second substrate.

In some implementations, the optical sensing apparatus can include alight emitter coupled to the third substrate. In some implementations,the first circuitry further comprises driver circuitry for a lightemitter.

In some implementations, one of more operating characteristics of thefirst circuitry is dependent on the absorption region, and one of moreoperating characteristics of the second circuitry is independent of theabsorption region.

In some implementations, the digital output is used for proximitysensing, imaging, or time-of-flight sensing.

Another example aspect of the present disclosure is directed to anoptical sensing apparatus that includes a first substrate comprising afirst material; an absorption region formed on or at least partially inthe first substrate, where the absorption region comprises a secondmaterial, and where the absorption region is configured to receive anoptical signal and to generate a photo-current in response to receivingthe optical signal; a second substrate bonded to the first substrate,where the second substrate comprises the first material; and firstcircuitry formed in the second substrate, where the first circuitry isconfigured to convert the photo-current and to an analog voltage outputfor processing.

In some implementations, the optical sensing apparatus can include athird substrate comprising second circuitry configured to process theanalog voltage output to generate a digital output, where the secondsubstrate is bonded to the third substrate, where the second substrateis arranged between the first substrate and the third substrate, andwhere the first substrate is arranged to receive the optical signal.

In some implementations, one of more operating characteristics of thefirst circuitry is dependent on the absorption region, and one of moreoperating characteristics of the second circuitry is independent of theabsorption region. In some implementations, the first circuitry furthercomprises driver circuitry for a light emitter.

Another example aspect of the present disclosure is directed to anoptical sensing apparatus that includes a photodetector. Thephotodetector includes a first substrate comprising a first material; apixel array having multiple pixels formed on or at least partially inthe first substrate, where the pixel array comprises a second material,where the pixel array is configured to receive an optical signal and togenerate a photo-current in response to receiving the optical signal,and where the multiple pixels of the array of pixels are electricallycoupled together to generate the photo-current; a second substratebonded to the first substrate, where the second substrate comprises thefirst material; and first circuitry formed in the second substrate,where the first circuitry is configured to convert the photo-current andto an analog voltage output for processing; and a third substratecoupled to the photodetector, where the third substrate comprisingsecond circuitry is configured to process the analog voltage output togenerate a digital output.

These and other objectives of the present disclosure will no doubtbecome obvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisapplication will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

FIGS. 1A-1D illustrate cross-sectional views of a photo-detectingdevice, according to some embodiments.

FIGS. 2A-2D illustrate cross-sectional views of a photo-detectingdevice, according to some embodiments.

FIGS. 2E-2F show schematic diagrams of circuits of a photo-detectingapparatus, according to some embodiments.

FIG. 3A illustrates a top view of a photo-detecting device, according tosome embodiments.

FIG. 3B illustrates a cross-sectional view along an A-A′ line in FIG.3A, according to some embodiments.

FIG. 4A illustrates a top view of a photo-detecting device, according tosome embodiments.

FIG. 4B illustrates a cross-sectional view along an A-A′ line in FIG.4A, according to some embodiments.

FIG. 4C illustrates a cross-sectional view along a B-B′ line in FIG. 4A,according to some embodiments.

FIG. 5A illustrates a top view of a photo-detecting device, according tosome embodiments.

FIG. 5B illustrates a cross-sectional view along an A-A′ line in FIG.5A, according to some embodiments.

FIG. 5C illustrates a cross-sectional view along a B-B′ line in FIG. 4A,according to some embodiments.

FIG. 6A illustrates a top view of a photo-detecting device, according tosome embodiments.

FIG. 6B illustrates a cross-sectional view along an A-A′ line in FIG.6A, according to some embodiments.

FIG. 6C illustrates a top view of a photo-detecting device, according tosome embodiments.

FIG. 6D illustrates a cross-sectional view along an A-A′ line in FIG.6C, according to some embodiments.

FIG. 6E illustrates a cross-sectional view along a B-B′ line in FIG. 6C,according to some embodiments.

FIG. 6F illustrates a top view of a photo-detecting device, according tosome embodiments.

FIG. 6G illustrates a top view of a photo-detecting device, according tosome embodiments.

FIG. 7A illustrates a top view of a photo-detecting device, according tosome embodiments.

FIG. 7B illustrates a cross-sectional view along an A-A′ line in FIG.7A, according to some embodiments.

FIGS. 7C-7E illustrate top views of a photo-detecting device, accordingto some embodiments.

FIG. 8A illustrates a top view of a photo-detecting device, according tosome embodiments.

FIG. 8B illustrates a cross-sectional view along an A-A′ line in FIG.8A, according to some embodiments.

FIGS. 8C-8E illustrate top views of a photo-detecting device, accordingto some embodiments.

FIGS. 9A-9B show schematic diagrams of circuits of a photo-detectingapparatus, according to some embodiments.

FIG. 10A illustrates a cross-sectional view of a photo-detecting device,according to some embodiments.

FIG. 10B illustrates a top view of a photo-detecting device, accordingto some embodiments.

FIG. 10C illustrates a cross-sectional view along an A-A′ line in FIG.10B, according to some embodiments.

FIG. 10D illustrates a top view of a photo-detecting device, accordingto some embodiments.

FIG. 10E illustrates a cross-sectional view along an A-A′ line in FIG.10D, according to some embodiments.

FIG. 10F illustrates a cross-sectional view along a B-B′ line in FIG.10D, according to some embodiments.

FIG. 10G illustrates a cross-sectional view of a photo-detecting device,according to some embodiments.

FIG. 10H illustrates a cross-sectional view of a photo-detecting device,according to some embodiments.

FIG. 10I illustrates a cross-sectional view of a photo-detecting device,according to some embodiments.

FIG. 11A illustrates a cross-sectional view of a photo-detecting device,according to some embodiments.

FIG. 11B illustrates a top view of a photo-detecting device, accordingto some embodiments.

FIG. 11C illustrates a cross-sectional view along an A-A′ line in FIG.11B, according to some embodiments.

FIG. 11D illustrates a top view of a photo-detecting device, accordingto some embodiments.

FIG. 11E illustrates a cross-sectional view along an A-A′ line in FIG.11D, according to some embodiments.

FIGS. 12A-12C illustrate cross-sectional views of the absorption regionof a photo-detecting device, according to some embodiments.

FIG. 13A illustrates a top view of a photo-detecting device, accordingto some embodiments.

FIG. 13B illustrates a top view of a photo-detecting device, accordingto some embodiments.

FIG. 14A illustrates a cross-sectional view of a portion of thephoto-detecting device, according to some embodiments.

FIG. 14B illustrates a cross-sectional view along a line passing seconddoped region 108 of the photo-detecting device, according to someembodiments.

FIG. 14C illustrates a top view of a photo-detecting device, accordingto some embodiments.

FIG. 14D illustrates a cross-sectional view along an A-A′ line in FIG.14B, according to some embodiments.

FIG. 14E illustrates a cross-sectional view along a B-B′ line in FIG.14B, according to some embodiments.

FIG. 14F illustrates a cross-sectional view of a photo-detecting device,according to some embodiments.

FIG. 14G illustrates a top view of a photo-detecting device, accordingto some embodiments.

FIG. 14H illustrates a cross-sectional view along an A-A′ line in FIG.14G, according to some embodiments.

FIG. 14I illustrates a cross-sectional view along a B-B′ line in FIG.14G, according to some embodiments.

FIG. 14J illustrates a top view of a photo-detecting device, accordingto some embodiments.

FIG. 14K illustrates a cross-sectional view along an A-A′ line in FIG.14J, according to some embodiments.

FIG. 14L illustrates a cross-sectional view along a B-B′ line in FIG.14J, according to some embodiments.

FIGS. 15A-15D show examples of a gain component with two terminals.

FIGS. 16A-16D show examples of a gain component with three terminals.

FIGS. 17A-17C show examples of a photo-detecting apparatus that can beused as a complementary metal-oxide-semiconductor (CMOS) image sensor.

FIGS. 18A-C show examples of a photo-detecting apparatus that can beused as a CMOS image sensor.

FIG. 19A shows a photo-detecting apparatus with gain.

FIG. 19B shows a photo-detecting apparatus with gain.

FIG. 20A shows an example top view of the photo-detecting apparatus withgain.

FIG. 20B shows an example top view of the photo-detecting apparatus withgain.

FIG. 21 shows a photo-detecting apparatus with gain.

FIG. 22A shows an example top view of the photo-detecting apparatus withgain.

FIG. 22B shows an example top view of the photo-detecting apparatus withgain.

FIG. 23A shows an example top view of the photo-detecting apparatus withgain.

FIG. 23B shows another example top view of the photo-detecting apparatuswith gain.

FIG. 24A shows an example top view of the photo-detecting apparatus withgain.

FIG. 24B shows another example top view of the photo-detecting apparatuswith gain.

FIGS. 25A-25C illustrate cross-sectional views of a portion of aphoto-detecting device.

FIGS. 26A-26D show the examples of the control regions of aphoto-detecting device according to some embodiments.

FIG. 27A is a block diagram of an example embodiment of an imagingsystem.

FIG. 27B shows a block diagram of an example receiver unit or thecontroller.

FIGS. 28-31 illustrate exemplary embodiments of an optical sensingapparatus, according to example aspects of the present disclosure.

FIGS. 32A-32C illustrate cross-sectional views of an optical sensingapparatus with micro-lens, according to example aspects of the presentdisclosure.

DETAILED DESCRIPTION

As used herein, the terms such as “first”, “second”, “third”, “fourth”and “fifth” describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms may be onlyused to distinguish one element, component, region, layer or sectionfrom another. The terms such as “first”, “second”, “third”, “fourth” and“fifth” when used herein do not imply a sequence or order unless clearlyindicated by the context. The terms “photo-detecting”, “photo-sensing”,“light-detecting”, “light-sensing” and any other similar terms can beused interchangeably.

Spatial descriptions, such as “above”, “top”, and “bottom” and so forth,are indicated with respect to the orientation shown in the figuresunless otherwise specified. It should be understood that the spatialdescriptions used herein are for purposes of illustration only, and thatpractical implementations of the structures described herein can bespatially arranged in any orientation or manner, provided that themerits of embodiments of this disclosure are not deviated by sucharrangement.

As used herein, the term “intrinsic” means that the semiconductormaterial is without intentionally adding dopants.

FIG. 1A illustrates a cross-sectional view of a photo-detecting device100 a, according to some embodiments. The photo-detecting device 100 aincludes an absorption region 10 and a substrate 20 supporting theabsorption region 10. In some embodiments, the absorption region 10 isentirely embedded in the substrate 20. In some embodiments, theabsorption region 10 is partially embedded in the substrate 20. In someembodiments, the photo-detecting device 100 a includes at least oneheterointerface between the absorption region 10 and a carrierconducting layer including or be composed of a material different fromthat of the absorption region 10. In some embodiments, the carrierconducting layer is the substrate 20. For example, in some embodiments,the substrate 20 includes a first surface 21 and a second surface 22opposite to the first surface 21. In some embodiments, the absorptionregion 10 includes a first surface 11, a second surface 12 and one ormore side surfaces 13. The second surface 12 is between the firstsurface 11 of the absorption region 10 and the second surface 22 of thesubstrate 20. The side surfaces 13 are between the first surface 11 ofthe absorption region 10 and the second surface 12 of the absorptionregion 10. At least one of the first surface 11, second surface 12 andthe side surfaces 13 of the absorption region 10 is at least partiallyin direct contact with the substrate 20 and thus the heterointerface isformed between the absorption region 10 and the substrate 20.

In some embodiments, the absorption region 10 is doped with aconductivity type and includes a first dopant having a first peak dopingconcentration. In some embodiments, the absorption region 10 isconfigured to convert an optical signal, for example, an incident light,to an electrical signal. In some embodiments, the optical signal entersthe absorption region 10 from the first surface 21 of the substrate 20.In some embodiments, the optical signal enters the absorption region 10from the second surface 22 of the substrate 20. In some embodiments, theabsorption region 10 includes an absorbed region AR, which is defined bya light shield (not shown) including an optical window. The absorbedregion AR is a virtual area receiving an optical signal incoming throughthe optical window.

In some embodiments, the carrier conducting layer, that is the substrate20 in some embodiments, is doped with a conductivity type and includes asecond dopant having a second peak doping concentration lower than thefirst peak doping concentration to reduce the dark current of thephoto-detecting device 100 a, which may improve the signal-to-noiseratio, sensitivity, dynamic range properties of the photo-detectingdevice 100 a.

In some embodiments, the first peak doping concentration is equal to orgreater than 1×10¹⁶ cm⁻³. In some embodiments, the first peak dopingconcentration can be between 1×10¹⁶ cm⁻³ and 1×10²⁰ cm³. In someembodiments, the first peak doping concentration can be between 1×10¹⁷cm⁻³ and 1×10²⁰ cm³. In some embodiments, a ratio of the first peakdoping concentration to the second peak doping concentration is equal toor greater than 10 such that the photo-detecting device 100 a canfurther achieve low dark current. In some embodiments, a ratio of thefirst peak doping concentration to the second peak doping concentrationis equal to or greater than 100 such that the photo-detecting device 100a can achieve further low dark current and high quantum efficiency atthe same time. In some embodiments, the conductivity type of thesubstrate 20 is p-type or n-type. In some embodiments, if theconductivity type of the substrate 20 is p-type, e.g., using boron (B)and/or gallium (Ga) as dopant, the second peak doping concentration canbe between 1×10¹² cm³ and 1×10¹⁶ cm⁻³ such that the photo-detectingdevice 100 a is can achieve low dark current and high quantum efficiencyat the same time. In some embodiments, if the conductivity type of thesubstrate 20 is of n-type, e.g., using phosphorus (P) and/or arsenic(As) as dopant, the second peak doping concentration can be between1×10¹⁴ cm³ and 1×10¹⁸ cm³ such that the photo-detecting device 100 a canachieve with low dark current and high quantum efficiency at the sametime.

In some embodiments, when the conductivity type of the carrierconducting layer, that is the substrate 20 in some embodiments, isdifferent from the conductivity type of the absorption region 10, and byhaving the second peak doping concentration of the substrate 20 lowerthan the first peak doping concentration of the absorption region 10, adepletion region is across the heterointerface between the substrate 20and the absorption region 10. A major part of the depletion region is inthe substrate 20 when the photo-detecting device is in operation. Inother words, a first width of the depletion region in the substrate 20is greater than a second width of the depletion region in the absorptionregion 10. In some embodiments, a ratio of the first width to the secondwidth is greater than 10. In some embodiments, a built-in electricalfield region is across an heterointerface between the substrate 20 andthe absorption region 10, where a first width of the built-in electricalfield region in the substrate 20 is greater than a second width of thebuilt-in electrical field region in the absorption region 10 so that thedark current is generated mostly from the substrate 20. Therefore, thephoto-detecting device can achieve lower dark current. In someembodiments, a bandgap of the carrier conducting layer, that is thesubstrate 20, is greater than a bandgap of the absorption region 10.

In some embodiments, when the conductivity type of the carrierconducting layer, that is the substrate 20 in some embodiments, is thesame as the conductivity type of the absorption region 10, such as whenthe substrate 20 is of p-type and the absorption region 10 is of p-type,by having the second peak doping concentration of the substrate 20 lowerthan the first peak doping concentration of the absorption region 10,the electric field across the absorption region 10 can be reduced andthus the electric field across the substrate 20 is increased. That is, adifference between the electric field across the absorption region 10and the electric field across the substrate 20 presents. As a result,the dark current of the photo-detecting device is further lower. In someembodiments, a bandgap of the carrier conducting layer, that is thesubstrate 20, is greater than a bandgap of the absorption region 10.

The carrier conducting layer, that is the substrate 20 in someembodiments, includes a first doped region 102 separated from theabsorption region 10. The first doped region 102 is doped with aconductivity type and includes a third dopant having a third peak dopingconcentration. The conductivity type of the first doped region 102 isdifferent from the conductivity type of the absorption region 10. Insome embodiments, the third peak doping concentration is higher than thesecond peak doping concentration. In some embodiments, the third peakdoping concentration of the first doped region 102 can be between 1×10¹⁸cm⁻³ and 5×10²⁰ cm⁻³.

In some embodiments, at least 50% of the absorption region 10 is dopedwith a doping concentration of the first dopant equal to or greater than1×10¹⁶ cm⁻³. In other words, at least half of the absorption region 10is intentionally doped with the first dopant having a dopingconcentration equal to or greater than 1×10¹⁶ cm⁻³. For example, a ratioof the depth of the doping region in the absorption region 10 to thethickness of the absorption region 10 is equal to or greater than 1/2.In some embodiments, at least 80% of the absorption region 10 isintentionally doped with the first dopant having a doping concentrationequal to or greater than 1×10¹⁶ cm⁻³ for further reducing the darkcurrent of the photo-detecting device. For example, a ratio of the depthof the doping region in the absorption region 10 to the thickness of theabsorption region 10 is equal to or greater than 4/5.

In some embodiments, the carrier conducting layer, can be majorly dopedwith the second dopant. For example, at least 50% of the carrierconducting layer, that is the substrate 20 in some embodiments, has adoping concentration of the second dopant equal to or greater than1×10¹² cm⁻³. In other words, at least half of the carrier conductinglayer is intentionally doped with the second dopant having a dopingconcentration equal to or greater than 1×10¹² cm⁻³. For example, a ratioof the depth of the doping region in the substrate 20 to the thicknessof the substrate 20 is equal to or greater than 1/2. In someembodiments, at least 80% of the carrier conducting layer, isintentionally doped with the second dopant having a doping concentrationequal to or greater than 1×10¹² cm⁻³. For example, a ratio of the depthof the doping region in the substrate 20 to the thickness of thesubstrate 20 is equal to or greater than 4/5.

In some embodiments, the carrier conducting layer can be regionallydoped with the second dopant. For example, the carrier conducting layer,that is the substrate 20 in some embodiments, includes a conductingregion 201. At least a part of the conducting region 201 is between thefirst doped region 102 and the absorption region 10. In someembodiments, the conducting region 201 is partially overlapped with theabsorption region 10 and the first doped region 102 for confining a pathof the carriers generated from the absorption region 10 moving towardsthe first doped region 102. In some embodiments, the conducting region201 has a depth measured from the first surface 21 of the substrate 20along a direction D1 substantially perpendicular to the first surface 21of the substrate 20. The depth is to a position where the dopant profileof the second dopant reaches a certain concentration, such as aconcentration between 1×10¹⁴ cm³ and 1×10¹⁵ cm⁻³. In some embodiments,the depth of the conducting region 201 is less than 5 μm for betterefficiently transporting the carriers. In some embodiments, theconducting region 201 may be overlapped with the entire first dopedregion 10. In some embodiments, the conducting region 201 has a widthgreater than a width of the absorption region 10.

In some embodiments, the first dopant and the second dopant aredifferent, for example, the first dopant is boron, and the second dopantis phosphorous. In some embodiments, a doping concentration of the firstdopant at the heterointerface between the absorption region 10 and thecarrier conducting layer, that is the substrate 20 in some embodiment,is equal to or greater than 1×10¹⁶ cm³. In some embodiments, the dopingconcentration of the first dopant at the heterointerface can be between1×10¹⁶ cm³ and 1×10²⁰ cm³ or between 1×10¹⁷ cm³ and 1×10²⁰ cm⁻³. In someembodiments, a doping concentration of the second dopant at theheterointerface is lower than the doping concentration of the firstdopant at the heterointerface. In some embodiments, a dopingconcentration of the second dopant at the heterointerface between 1×10¹²cm⁻³ and 1×10¹⁷ cm⁻³.

In some embodiments, since the doping concentration of the first dopantat the heterointerface is sufficiently high, it may reduce the interfacedark current generation at the heterointerface. As a result, theinterface combination velocity can be reduced and thus the dark currentat the heterointerface can be lower. In some embodiments, since thedoping concentration of the second dopant at the heterointerface islower than the doping concentration of the first dopant at theheterointerface, the bulk dark current generation in the absorptionregion 10 is also reduced. In some embodiments, the photo-detectingdevice 100 a can have an interface recombination velocity lower than 10⁴cm/s.

In some embodiments, a ratio of the doping concentration of the firstdopant to the doping concentration of the second dopant at theheterointerface is equal to or greater than 10 such that thephoto-detecting device 100 a can achieve low dark current at theheterointerface and high quantum efficiency at the same time. In someembodiments, a ratio of the doping concentration of the first dopant tothe doping concentration of the second dopant at the heterointerface isequal to or greater than 100 such that the photo-detecting device 100 acan exhibit further low dark current at the heterointerface and highquantum efficiency at the same time.

In some embodiments, the second dopant may be in the absorption region10, but also may present outside the absorption region 10 due to thermaldiffusion or implant residual etc. In some embodiments, the first dopantmay be in the carrier conducting layer, that is the substrate 20 in someembodiments, but also may present outside the substrate region 20 due tothermal diffusion or implant residual etc.

In some embodiments, the first dopant may be introduced in theabsorption region 10 by any suitable process, such as in-situ growth,ion implantation, and/or thermal diffusion etc.

In some embodiments, the second dopant may be introduced in thesubstrate 20 by any suitable process, such as in-situ growth, ionimplantation, and/or thermal diffusion etc.

In some embodiments, the absorption region 10 is made by a firstmaterial or a first material-composite. The carrier conducting layer,that is the substrate 20 in some embodiments, is made by a secondmaterial or a second material-composite. The second material or a secondmaterial-composite is different from the first material or a firstmaterial-composite. For example, in some embodiments, the combinationsof elements of second material or a second material-composite isdifferent from the combinations of elements in the first material or afirst material-composite.

In some embodiments, a bandgap of the carrier conducting layer, that isthe substrate 20 in some embodiments, is greater than a bandgap of theabsorption region 10. In some embodiments, the absorption region 10includes or is composed of a semiconductor material. In someembodiments, the substrate 20 includes or is composed of a semiconductormaterial. In some embodiments, the absorption region 10 includes or iscomposed of a Group III-V semiconductor material. In some embodiments,the substrate 20 includes or is composed of a Group III-V semiconductormaterial. The Group III-V semiconductor material may include, but is notlimited to, GaAs/AlAs, InP/InGaAs, GaSb/InAs, or InSb. For example, insome embodiments, the absorption region 10 includes or is composed ofInGaAs, and the substrate 20 include or is composed of InP. In someembodiments, the absorption region 10 includes or is composed of asemiconductor material including a Group IV element. For example, Ge, Sior Sn. In some embodiments, the absorption region 10 includes or iscomposed of the Si_(x)Ge_(y)Sn_(1-x-y), where 0≤x≤1, 0≤y≤1, 0≤x+y≤1. Insome embodiments, the absorption region 10 includes or is composed ofGe_(1-a)Sn_(a), where 0≤a≤0.1. In some embodiments, the absorptionregion 10 includes or is composed of Ge_(x)Si_(1-x), where 0≤x≤1. Insome embodiments, the absorption region 10 composed of intrinsicgermanium is of p-type due to material defects formed during formationof the absorption region, where the defect density is from 1×10¹⁴ cm⁻³to 1×10¹⁶ cm⁻³. In some embodiments, the carrier conducting layer, thatis the substrate 20 in some embodiments, includes or is composed of asemiconductor material including a Group IV element. For example, Ge, Sior Sn. In some embodiments, the substrate 20 includes or is composed ofthe Si_(x)Ge_(y)Sn_(1-x-y), where 0≤x≤1, 0≤y≤1, 0≤x+y≤1. In someembodiments, the substrate 20 includes or is composed of Ge_(1-a)Sn_(a),where 0≤a≤0.1. In some embodiments, the substrate 20 includes or iscomposed of Ge_(x)S_(1-x), where 0≤x≤1. In some embodiments, thesubstrate 20 composed of intrinsic germanium is of p-type due tomaterial defects formed during formation of the absorption region, wherethe defect density is from 1×10¹⁴ cm³ to 1×10¹⁶ cm⁻³. For example, insome embodiments, the absorption region 10 includes or is composed ofGe, and the substrate 20 include or is composed of Si.

In some embodiments, the conductivity type of the absorption region 10is p-type. In some embodiments, the first dopant is a Group III element.In some embodiments, the conductivity type of the substrate 20 isn-type, the second dopant is a Group V element.

In some embodiments, the photo-detecting device includes a firstelectrode 30 electrically coupled to the first doped region 102. Thefirst electrode 30 is separated from the absorption region 10. An ohmiccontact may be formed between the first electrode 30 and the first dopedregion 102 depending on the material of the first electrode 30 and thethird peak doping concentration of the first doped region 102. In someembodiments, a nearest distance d between the first electrode 30 and oneof the side surfaces 13 of the absorption region can be between 0.1 μmand 20 μm. In some embodiments, a nearest distance d between the firstelectrode 30 and one of the side surfaces 13 of the absorption regioncan be between 0.1 μm and 5 μm. In some embodiments, the distance can bebetween 0.5 μm and 3 μm. If the distance d between the first electrode30 and the side surfaces 13 is greater than 20 μm, the speed of thephoto-detecting device 100 a is lower. If the distance d between thefirst electrode 30 and the side surfaces 13 is less than 0.1 μm, thedark current of the photo-detecting device may be increased.

In some embodiments, the photo-detecting device 100 a includes a seconddoped region 108 in the absorption region 10 and near the first surface11 of the absorption region 10. The second doped region 108 is dopedwith a conductivity type the same as the conductivity type of theabsorption region 10. In some embodiments, the second doped region 108includes a fourth dopant having a fourth peak doping concentrationhigher than the first peak doping concentration. For example, the fourthpeak doping concentration of the second doped region 108 can be between1×10¹⁸ cm⁻³ and 5×10²⁰ cm⁻³. In some embodiments, the second dopedregion 108 is not arranged over the first doped region 102 along thedirection D1.

In some embodiments, the photo-detecting device 100 a further includes asecond electrode 60 electrically coupled to the second doped region 108.An ohmic contact may be formed between the second electrode 60 and thesecond doped region 108 depending on the material of the secondelectrode 60 and the fourth peak doping concentration of the seconddoped region 108. The second electrode 60 is over the first surface 11of the absorption region 10.

In some embodiments, the carrier conducting layer includes a firstsurface and a second surface opposite to the first surface 21. The firstelectrode 30 and second electrode 60 are both disposed over the of thefirst surface of the carrier conducting layer. That is, the firstelectrode 30 and second electrode 60 are disposed over a same side ofthe carrier conducting layer, that is the substrate 20 in someembodiment, which is benefit for the backend fabrication processafterwards.

The first doped region 102 and the second doped region 108 can besemiconductor contact regions. In some embodiments, depending on thecircuits electrically coupled to the first doped region 102 and thesecond doped region 108, the carriers with a first type collected by oneof the first doped region 102 and the second doped region 108 can befurther processed, and the carriers with second type collected by theother doped region can be evacuated. Therefore, the photo-detectingdevice can have improved reliability and quantum efficiency.

In some embodiments, the absorption region 10 is doped with a gradeddoping profile. In some embodiments, the largest concentration of thegraded doping profile is higher than the second peak dopingconcentration of the second dopant. In some embodiments, the smallestconcentration of the graded doping profile is higher than the secondpeak doping concentration of the second dopant. In some embodiments, thegraded doping profile can be graded from the first surface 11 of theabsorption region 10 or from the second doped region 108 to the secondsurface 12 of the absorption region 10. In some embodiments, the gradeddoping profile can be a gradual decrease/increase or a step likedecrease/increase depending on the moving direction of the carriers. Insome embodiments, the concentration of the graded doping profile isgradually deceased/increased from the first surface 11 or the seconddoped region 108 of the absorption region 10 to the second surface 12 ofthe absorption region 10 depending on the moving direction of thecarriers. In some embodiments, the concentration of the graded dopingprofile is gradually and radially deceased/increased from a center ofthe first surface 11 or the second doped region 108 of the absorptionregion 10 to the second surface 12 and to the side surfaces 13 of theabsorption region 10 depending on the moving direction of the carriers.For example, if the absorption region 10 is entirely over the substrate20, the carriers with the first type, such as electrons when the firstdoped region 102 is of n-type, move in the absorption region 10substantially along a direction from the first surface 11 to the secondsurface 12, the concentration of the graded doping profile of the firstdopant, for example, boron, is gradually deceased from the first surface11 or from the second doped region 108 of the absorption region 10 tothe second surface 12 of the absorption region 10. In some embodiments,the concentration of the graded doping profile is gradually andlaterally decreased/increased from an edge of the first surface 11 orthe second doped region 108 of the absorption region 10 to the sidesurfaces 13 of the absorption region 10 depending on the movingdirection of the carriers.

In some embodiments, the dark current of the photo-detecting device isabout several pA or lower, for example, lower than 1×10⁻¹² A.

FIG. 1B illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 100 b in FIG.1B is similar to the photo-detecting device 100 a in FIG. 1A. Thedifference is described below.

The photo-detecting device 100 b further includes another first dopedregion 104 in the substrate 20. The first doped region 104 is similar tothe first doped region 102 as described in FIG. 1A. The first dopedregion 104 is separated from the absorption region 10. At least a partof the conducting region 201 is also between the first doped region 104and the absorption region 10. In some embodiments, the conducting region201 is partially overlapped with the absorption region 10 and the firstdoped region 104 for confining a path of the carriers with a first typegenerated from the absorption region 10 moving towards the first dopedregion 104.

In some embodiments, the two first doped regions 104, 102 are separatedfrom each other. In some embodiments, the two first doped regions 104,102 may be a continuous region, for example, a ring. The photo-detectingdevice 100 b further includes a third electrode 40 electrically coupledto the first doped region 104. In some embodiment, the first electrode30 and the third electrode 40 may be electrically coupled to the samecircuit.

In some embodiments, the dark current of the photo-detecting device 100b is about several pA or lower, for example, lower than 1×10⁻¹² A.

A photo-detecting device in accordance to a comparative example includesstructures substantially the same as the structures of a photo-detectingdevice 100 b in FIG. 1B. The difference is that in the photo-detectingdevice of the comparative example, the doping concentration of theabsorption region 10 is not higher than the second peak dopingconcentration of the substrate 20, and the doping concentration of thesecond dopant at the heterointerface is not lower than the dopingconcentration of the first dopant at the heterointerface

The details of the photo-detecting device in accordance to a comparativeexample and the photo-detecting device 100 b are listed in Table 1 andTable 2.

TABLE 1 Details of the photo-detecting device in accordance to acomparative example Conductivity type of the absorption region p-type,First peak doping concentration 1 × 10¹⁵ cm − 3 Conductivity type of thesubstrate n-type Second peak doping concentration 1 × 10¹⁵ cm − 3Reference dark current 100%

TABLE 2 Details of the photo-detecting device 100b Conductivity type ofthe absorption region p-type, First peak doping concentration Referringto Table 3 Conductivity type of the substrate n-type Second peak dopingconcentration 1 × 10¹⁵ cm − 3 Dark current Referring to Table 3

Referring to Table 3, compared to the comparative example, since thefirst peak doping concentration of the absorption region 10 in thephoto-detecting device 100 b is higher than the second peak dopingconcentration of the substrate 20, the photo-detecting device 100 b canhave lower dark current, for example, at least two times lower.

TABLE 3 Dark current vs. First peak doping concentration ofphoto-detecting device 100b in accordance to different embodiments Darkcurrent first peak doping (compared to the reference dark concentrationcurrent in comparative example) 1.00E+16    42% 1.00E+17  0.29% 1.00E+180.0052% 1.00E+19  0.001%

Another photo-detecting device in accordance to a comparative exampleincludes structures substantially the same as the structures of aphoto-detecting device 100 b in FIG. 1B. The difference is that the inthe other photo-detecting device of the comparative example, the dopingconcentration of the absorption region 10 is not higher than the secondpeak doping concentration of the substrate 20, and the dopingconcentration of the second dopant at the heterointerface is not lowerthan the doping concentration of the first dopant at theheterointerface. The details of the other photo-detecting device inaccordance to a comparative example and the photo-detecting device 100 bare listed in Table 4 and Table 5.

TABLE 4 Details of the other photo-detecting device in accordance to acomparative example Conductivity type of the absorption region p-type,First peak doping concentration 1 × 10¹⁵ cm − 3 Conductivity type of thesubstrate p-type Second peak doping concentration 1 × 10¹⁵ cm − 3Reference dark current 100%

TABLE 5 Details of the photo-detecting device 100b Conductivity type ofthe absorption region p-type First peak doping concentration Referringto Table 6 Conductivity type of the substrate p-type Second peak dopingconcentration 1 × 10¹⁵ cm − 3 Dark current Referring to Table 6

Referring to Table 6, compared to the other comparative example, sincethe first peak doping concentration of the absorption region 10 in thephoto-detecting device 100 b is higher than the second peak dopingconcentration of the substrate 20, the photo-detecting device 100 b canhave lower dark current, for example, at least 20 times lower.

TABLE 6 Dark current vs. First peak doping concentration ofphoto-detecting device 100b in accordance to different embodiments Darkcurrent first peak doping (compared to the Reference dark concentrationcurrent in comparative example) 1.00E+16   4.6% 1.00E+17   0.1% 1.00E+18 0.01% 1.00E+19 0.0017%

FIG. 1C illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 100 c in FIG.1C is similar to the photo-detecting device 100 a in FIG. 1A. Thedifference is described below.

The substrate 20 includes a base portion 20 a and an upper portion 20 bsupporting by the base portion 20 a. The upper portion 20 b has a widthless than a width of the base portion 20 a. The absorption region 10 issupported by the upper portion 20 b of the substrate 20. The conductingregion 201 is in the upper portion 20 b. The first doped region 102 isin the base portion 20 a. The first doped region 102 has a width greaterthan the width of the upper portion 20 b of the substrate 20 and thus apart of the first doped region 102 is not covered by the upper portion20 b. The second doped region 108 is arranged over the first dopedregion 102 along the direction D1, and the conducting region 201 isbetween the first doped region 102 and the second doped region 108. Thecarriers with a first type generated from the absorption region 10, forexample, electrons, will move towards first doped region 102 through theconducting region 201 along the direction D1.

In some embodiments, the first electrode 30 may be in any suitableshape, such as a ring from a top view of the photo-detecting device. Insome embodiments, the photo-detecting device 100 c includes two firstelectrodes 30 electrically coupled to the first doped region 102 andseparated from each other. In some embodiments, the first electrodes 30are disposed at opposite sides of the absorption region 10.

In some embodiments, based on the reverse bias voltage applied to thesecond doped region 108 and the first doped region 102, if an impactionization occurs, the photo-detecting device 100 c can be an avalanchephotodiode operated in linear mode (reverse bias voltage<breakdownvoltage) or Geiger mode (reverse bias voltage>breakdown voltage), andthe portion of the conducting region 201 in between the absorptionregion 10 and the first doping region 102 can be a multiplicationregion. The multiplication region is then capable of generating one ormore additional charge carriers in response to receiving the one or morecarriers generated from the absorption region 10.

FIG. 1D illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 100 d in FIG.1D is similar to the photo-detecting device 100 c in FIG. 1C. Thedifference is described below.

The photo-detecting device 100 d further includes a charge layer 202 inthe upper portion 20 b of the substrate 20. The charge layer 202 is indirect contact with the absorption region 10 or overlapped with aportion of the absorption region 10. The charge layer 202 is of aconductivity type the same as the conductivity type of the absorptionregion 10. For example, if the conductivity type of the absorptionregion 10 is p, the conductivity type of the charge layer 202 is p. Thecharge layer 202 is with a peak doping concentration higher than thesecond peak doping concentration of the conducting region 201 and lowerthan the first peak doping concentration of the absorption region 10. Insome embodiments, the charge layer 202 is with a thickness between 10 nmand 500 nm. The charge layer can reduce the electric field across theabsorption region 10 and thus increase the electric field across theconducting region 201. That is, a difference between the electric fieldacross the absorption region 10 and the electric field across theconducting region 201 presents. As a result, the speed and theresponsivity of the photo-detecting device 100 d is also higher, and thedark current of the photo-detecting device 100 d is also lower.

FIG. 2A illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 200 a in FIG.2A is similar to the photo-detecting device 100 a in FIG. 1A. Thedifference is described below. The second doped region 108 is in thesubstrate 20. In other words, the fourth peak doping concentration ofthe second doped region 108 lies in the substrate 20. In someembodiment, the second doped region 108 is below the first surface 21 ofthe substrate 20 and is in direct contact with the absorption region 10,for example, the second doped region 108 may be in contact with oroverlapped with one of the side surfaces 13 of the absorption region 10.As a result, the carriers generated from the absorption region 10 canmove from the absorption region 10 towards the second doped region 108through the heterointerface between the absorption region 10 and thesubstrate 20. The second electrode 60 is over the first surface 21 ofthe substrate 20.

By having the second doped region 108 in the substrate 20 instead of inthe absorption region 10, the second electrode 60 and the firstelectrode 30 can both be formed above the first surface 21 of thesubstrate 20. Therefore, a height difference between the secondelectrode 60 and the first electrode 30 can be reduced and thus thefabrication process afterwards will be benefit from this design.Besides, the area of the absorption region 10 absorbing the opticalsignal can be larger.

FIG. 2B illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 200 b in FIG.2B is similar to the photo-detecting device 200 a in FIG. 2A. Thedifference is described below. The second doped region 108 can be alsoin contact with or overlapped with the second surface 12 of theabsorption region 10.

FIG. 2C illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 200 c in FIG.2C is similar to the photo-detecting device 200 b in FIG. 2B. Thedifference is described below. The absorption region 10 is entirely overthe substrate 20. A part of the second doped region 108 is covered bythe absorption region 10. In some embodiments, a width w2 of the seconddoped region 108 covered by the absorption region 10 may be greater than0.2 μm. In some embodiments, the absorption region 10 has a width w1.The width w₂ is not greater than 0.5 w₁. By this design, two differenttypes of the carriers can move from the absorption region 10 to thefirst doped region 102 and from the absorption region 10 to the seconddoped region 108 respectively without obstruction.

FIG. 2D illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 200 d in FIG.2D is similar to the photo-detecting device 200 a in FIG. 2A. Thedifference is described below. The absorption region 10 is entirelyembedded in the substrate 20. In some embodiments, the graded dopingprofile of the first dopant is gradually and laterally decreased fromthe side surface 13 near the second doped region 108 to the side surface13 near the conducting region 201. FIG. 2E shows a schematic diagram ofa photo-detecting apparatus, according to some embodiments. Thephoto-detecting apparatus 200 e includes a pixel (not labeled) and acolumn bus electrically coupled to the pixel. The pixel includes aphoto-detecting device and a readout circuit (not labeled) electricallycoupled to the photo-detecting device and the column bus. Thephoto-detecting device can be any photo-detecting device in FIG. 1Athrough FIG. 1D and FIG. 2A through FIG. 2D, for example, thephoto-detecting device 100 a in FIG. 1A. In some embodiments, thereadout circuit (not labeled) and the column bus may be fabricated onanother substrate and integrated/co-packaged with the photo-detectingdevice via die/wafer bonding or stacking. In some embodiments, thephoto-detecting apparatus 200 e includes a bonding layer (not shown)between the readout circuit and the photo-detecting device. The bondinglayer may include any suitable material such as oxide or semiconductoror metal or alloy.

In some embodiments, the readout circuit can be electrically coupled tothe first doped region 102 or the second doped region 108 to process thecollected carriers with a first type, and a supply voltage or a groundvoltage can be applied to the other doped region to evacuate

other carriers with a second type opposite to the first type.

For example, if the first doped region 102 is of n-type and the seconddoped region 108 is of p-type, the readout circuit can be electricallycoupled to the first doped region 102 for processing the collectedelectrons for further application, and a ground voltage can be appliedto the second doped region 108 to evacuate holes. For another example,the readout circuit can also be electrically coupled to the second dopedregion 108 for processing the collected holes for further application,and a supply voltage can be applied to the first doped region 102 toevacuate electrons.

In some embodiments, the readout circuit may be in a three-transistorconfiguration consisting of a reset gate, a source-follower, and aselection gate, or in a four-transistor configuration including anadditional transfer gate, or any suitable circuitry for processingcollected charges. For example, the readout circuit includes a transfertransistor 171A, a reset transistor 141A, a capacitor 150A coupled tothe reset transistor 141A, a source follower 142A, and a row selectiontransistor 143A. Examples of the capacitor 150A include, but not limitedto, floating-diffusion capacitors, metal-oxide-metal (MOM) capacitors,metal-insulator-metal (MIM) capacitors, and metal-oxide-semiconductor(MOS) capacitors.

The transfer transistor 171A transfers carriers from the photo-detectingdevice 100 a to the capacitor 150A. In other words, the transfertransistor 171A is configured to output the photo-current IA1 accordingto a switch signal TG1. When the switch signal TG1 turns on the transfertransistor 171A, the photo-current IA1 will be generated.

At the beginning, the reset signal RST resets the output voltage VOUT1to VDD. Then, when the switch signal TG1 turns on the transfertransistor 171A, the photo-current IA1 is generated, the output voltageVOUT1 on the capacitor 150A will drop until the switch signal TG1 turnsoff the transistor 171A.

In some other embodiments, the readout circuit may be fabricated onanother substrate and integrated/co-packaged with the photo-detectingdevice 100 a via die/wafer bonding or stacking. In some embodiments, thephoto-detecting apparatus is an CMOS image sensor is operated at a framerate not more than 1000 frames per second fps.

FIG. 2F shows a schematic diagram of circuits of a photo-detectingapparatus, according to some embodiments. The photo-detecting apparatus200 f is similar to the photo-detecting apparatus 200 e in FIG. 2E. Thedifference is described below.

The readout circuit of the photo-detecting apparatus 200 f furtherincludes a voltage-control transistor 130A between the transfertransistor 171A and the capacitor 150A. The voltage-control transistor130A is configured as a current buffer. Specifically, an output terminalof the voltage-control transistor 130A is coupled to the input terminalof the capacitor 150A, and the input terminal of the voltage-controltransistor 130A is coupled to the output terminal of the transistor171A. The control terminal of the voltage-control transistor 130A iscoupled to a control voltage VC1.

Since the voltage-control transistor 130A is coupled between thetransfer transistor 171A and the capacitor 150A, the output terminal ofthe transfer transistor 171A and the input terminal of capacitor 150Aare separated. When the voltage-control transistor 130A is operated in asubthreshold or saturation region, the output terminal of the transfertransistor 171A can be controlled or biased at a constant voltage VA1 toreduce the dark current generated by the photo-detecting device 100 a.

FIG. 3A illustrates a top view of a photo-detecting device, according tosome embodiments. FIG. 3B illustrates a cross-sectional view along anA-A′ line in FIG. 3A, according to some embodiments. The photo-detectingdevice includes an absorption region 10 and a substrate 20 supportingthe absorption region 10. The absorption region 10 is similar to theabsorption region 10 as described in FIG. 1A. The substrate 20 issimilar to the substrate 20 as described in FIG. 1A. The differencebetween the photo-detecting device 300 a in FIG. 3A and thephoto-detecting device 100 a in FIG. 1A is described below. Thephoto-detecting device 300 a includes a first switch (not labeled) and asecond switch (not labeled) electrically coupled to the absorptionregion 10 and partially formed in the carrier conducting layer, that isthe substrate 20 in some embodiments. The first switch includes acontrol region C1 including a control electrode 340 a. The first switchfurther includes a readout electrode 330 a separated from the controlelectrode 340 a. The second switch includes a control region C2including a control electrode 340 b. The second switch further includesa readout electrode 330 b separated from the control electrode 340 b. Insome embodiments, the readout electrodes 330 a, 330 b, and the controlelectrodes 340 a, 340 b are formed over a first surface 21 of thesubstrate 20 and are separated from the absorption region 10. In someembodiments, the readout electrode 330 a and the readout electrode 330 bare disposed at opposite sides of the absorption region 10. In someembodiments, a nearest distance between one of the control electrodesand the one or more side surfaces of the absorption region is between0.1 μm and 20 μm.

In some embodiments, a photo-detecting apparatus includes a pixelincluding the photo-detecting device 300 a as mentioned above, and thepixel further includes two control signals, for example, a first controlsignal and a second control signal, controlling the control regions C1,C2 respectively for controlling the moving direction of the electrons orholes generated by the absorbed photons in the absorption region 10. Insome embodiments, the first control signal is different from the secondcontrol signal. For example, when voltages are used, if one of thecontrol signals is biased against the other control signal, an electricfield is created between the two portions right under the controlelectrodes 340 a, 340 b as well as in the absorption region 10, and freecarriers in the absorption region 10 drift towards one of the portionsright under the readout electrodes 330 b 330 a depending on thedirection of the electric field. In some embodiments the first controlsignal includes a first phase, and the second control signal includessecond phase, where the first control phase is not overlapped with thesecond control phase. In some embodiments, the first control signal isfixed at a voltage value V, and the second control signal is alternatebetween voltage values V±ΔV. In some embodiments, ΔV is generated by avarying voltage signal, e.g., sinusoid signal, clock signal or pulsesignal operated between 0V and 3V. The direction of the bias valuedetermines the drift direction of the carriers generated from theabsorption region 10. The control signals are modulated signals.

In some embodiments, the first switch includes a first doped region 302a under the readout electrodes 330 a. The second switch includes a firstdoped region 302 b under the readout electrodes 330 b. In someembodiments, the first doped regions 302 a, 302 b are of a conductivitytype different from conductivity type of the absorption region 10. Insome embodiments, the first doped regions 302 a, 302 b include a dopantand a dopant profile with a peak dopant concentration. In someembodiments, the peak doping concentrations of the first doped regions302 a, 302 b are higher than the second peak doping concentration. Insome embodiments, the peak dopant concentrations of the first dopedregions 302 a, 302 b depend on the material of the readout electrodes330 a, 330 b and the material of the substrate 20, for example, can bebetween 5×10¹⁸ cm⁻³ to 5×10²⁰ cm⁻³. The first doped regions 302 a, 302 bare carrier collection regions for collecting the carriers with thefirst type generated from the absorption region 10 based on the controlof the two control signals.

In some embodiments, the absorption function and the carrier controlfunction such as demodulation of the carriers and collection of thecarriers operate in the absorption region 10 and the carrier conductinglayer, that is, the substrate 20 in some embodiments, respectively.

In some embodiments, the photo-detecting device 300 a may include asecond doped region 108 and a second electrode 60 similar to the seconddoped region 108 and the second electrode 60 respectively in FIG. 1A.The second doped region 108 is for evacuating the carriers of the secondtype opposite to the first type, which are not collected by the firstdoped regions 302 a, 302 b, during the operation of the photo-detectingdevice. In some embodiments, the control electrodes 340 a is symmetricto the control electrode 340 b with respect to an axis passing throughthe second electrode 60. In some embodiments, the readout electrode 330a is symmetric to the readout electrodes 330 b with respect to an axispassing through the second electrode 60. The control electrodes 340 a,340 b, the readout electrodes 330 a, 330 b and the second electrode 60are all disposed over the of the first surface of the carrier conductinglayer. That is, the control electrodes 340 a, 340 b, the readoutelectrodes 330 a, 330 b and the second electrode 60 are over a same sideof the carrier conducting layer, that is the substrate 20 in someembodiment.

In some embodiments, the substrate 20 of the photo-detecting device 300a includes a conducting region 201 similar to the conducting region 201as described in FIG. 1A. The difference is described below. In someembodiments, from a cross-sectional view of the photo-detecting device300 a, a width of the conducting region 201 can be greater than adistance between the two readout electrodes 330 a, 330 b. In someembodiments, the conducting region 201 is overlapped with the entirefirst doped regions 302 a, 302 b. In some embodiments, a width of theconducting region 201 can be less than a distance between the tworeadout electrodes 330 a, 330 b and greater than a distance between thetwo control electrodes 340 a, 340 b. In some embodiments, the conductingregion 201 is overlapped with a portion of first doped region 302 a anda portion of the first doped region 302 b. Since the conducting region201 is overlapped with at least a portion of first doped region 302 aand at least a portion of the first doped region 302 b, the carrierswith a first type that are generated from the absorption region 10 canbe confined in the conducting region 201 and move towards one of thefirst doped regions 302 a, 302 b based on the control of the two controlsignals. For example, if the first doped regions 302 a, 302 b are ofn-type, the conducting region 201 is of n-type, the second doped region108 is p-type, the electrons generated from the absorption region 10 canbe confined in the conducting region 201 and move towards one of thefirst doped regions 302 a, 302 b based on the control of the two controlsignals, and the holes can move towards the second doped region 108 andcan be further evacuated by a circuit.

In some embodiments, the photo-detecting apparatus includes a pixelarray including multiple repeating pixels. In some embodiments, thepixel array may be a one-dimensional or a two-dimensional array ofpixels.

A photo-detecting device in accordance to a comparative example includesstructures substantially the same as the structures of a photo-detectingdevice 300 a in FIG. 3A, the difference is that in the photo-detectingdevice of the comparative example, the doping concentration of theabsorption region 10 is not higher than the second peak dopingconcentration of the substrate 20 and the doping concentration of thesecond dopant at the heterointerface is not lower than the dopingconcentration of the first dopant at the heterointerface.

The details of the photo-detecting device in accordance to a comparativeexample and the photo-detecting device 300 a are listed in Table 7 andTable 8.

TABLE 7 Details of the photo-detecting device in accordance to acomparative example Conductivity type of the absorption region p-type,First peak doping concentration 1 × 10¹⁵ cm − 3 Conductivity type of thesubstrate n-type Second peak doping concentration 1 × 10¹⁵ cm − 3Reference photocurrent 1 × 10⁻⁶ A

TABLE 8 Details of the photo-detecting device 300a Conductivity type ofthe absorption region p-type, First peak doping concentration 1 × 10¹⁷cm⁻³ Conductivity type of the substrate n-type Second peak dopingconcentration 1 × 10¹⁵ cm − 3 Photo current Referring to Table 10

Referring to Table 9 and Table 10, compared to the comparative example,since the first peak doping concentration of the absorption region 10 inthe photo-detecting device 300 a is higher than the second peak dopingconcentration of the substrate 20, the photo-detecting device 300 a canhave lower dark current, for example, at least 100 times lower.

TABLE 9 Results of the comparative example second control readoutCurrent electrode electrode electrode measured at: 60 @ 0 V 330b @ 3.2 V340b @ 3.3 V Without ~L ~L ~D incident light With ~L ~L ~P incidentlight Unit: Arbitrary Unit

TABLE 10 Results of the photo-detecting device 300a second controlreadout Current electrode electrode electrode measured at: 60 @ 0 V 330b@ 3.2 V 340b @ 3.3 V Without ~10 L ~10 L ~0.01 D incident light With ~10L ~10 L  ~0.9 P incident light Unit: Arbitrary Unit

In some embodiments, a voltage can be applied to the second electrode60. In some embodiments, the voltage applied to the second electrode 60can reduce a leakage current between the second doped region 108 and thecontrol regions C1, C2. In some embodiment, the voltage is between thevoltage applied to the control electrode 340 a and the voltage appliedto the control electrode 340 b when operating the photo-detecting device300 a.

FIG. 4A illustrates a top view of a photo-detecting device, according tosome embodiments. FIG. 4B illustrates a cross-sectional view along anA-A′ line in FIG. 4A, according to some embodiments. FIG. 4C illustratesa cross-sectional view along a B-B′ line in FIG. 4A, according to someembodiments. The photo-detecting device 400 a in FIG. 4A is similar tothe photo-detecting device 300 a in FIG. 3A. The difference is describedbelow.

Referring to FIG. 4A and FIG. 4B, the second doped region 108 is in thesubstrate 20. In other words, the fourth peak doping concentration ofthe second doped region 108 lies in the substrate 20. The second dopedregion 108 is below the first surface 21 of the substrate 20 and is indirect contact with the absorption region 10, for example, the seconddoped region 108 may be in contact with or overlapped with one of theside surfaces 13 of the absorption region 10. As a result, the carrierswith the second type, which are not collected by the first doped regions302 a, 302 b, can move from the absorption region 10 towards the seconddoped region 108 through the heterointerface between the absorptionregion 10 and the substrate 20.

For example, if the first doped regions 302 a, 302 b are of n-type, theconducting region 201 is of n-type, the second doped region 108 isp-type, the electrons generated from the absorption region 10 can beconfined in the conducting region 201 and move towards one of the firstdoped regions 302 a, 302 b based on the control of the two controlsignals, and the holes can move towards the second doped region 108through the heterointerface between the absorption region 10 and thesubstrate 20 and can be further evacuated by a circuit.

The second electrode 60 is over the first surface 21 of the substrate20. By having the second doped region 108 in the substrate 20 instead ofin the absorption region 10, the second electrode 60, the readoutelectrodes 330 a, 330 b, and the control electrodes 340 a, 340 b can allbe coplanarly formed above the first surface 21 of the substrate 20.Therefore, a height difference between any two of the second electrode60 and the four electrodes 330 a, 330 b, 340 a, 340 b can be reduced andthus the fabrication process afterwards will be benefit from thisdesign. Besides, the area of the absorption region 10 absorbing theoptical signal can be larger.

FIG. 5A illustrates a top view of a photo-detecting device, according tosome embodiments. FIG. 5B illustrates a cross-sectional view along anA-A′ line in FIG. 5A, according to some embodiments. FIG. 5C illustratesa cross-sectional view along a B-B′ line in FIG. 5A, according to someembodiments. The photo-detecting device 500 a in FIG. 5A is similar tothe photo-detecting device 400 a in FIG. 4A. The difference is describedbelow. The readout electrodes 330 a, 330 b and the control electrodes340 a, 340 b are disposed at the same side of the absorption region 10,which improves the contrast ratio of the photo-detecting device 400 asince the carriers are forced to move out from the absorption region 10through one of the side surfaces 13. In some embodiments, the distancebetween the readout electrodes 330 a, 330 b along a direction Y can begreater than the distance between the control electrodes 340 a, 340 balong the direction Y. In some embodiments, the distance between thereadout electrodes 330 a, 330 b along a direction Y can be substantiallythe same as the distance between the control electrodes 340 a, 340 balong the direction Y.

FIG. 6A illustrates a top view of a photo-detecting device, according tosome embodiments. FIG. 6B illustrates a cross-sectional view along anA-A′ line in FIG. 6A, according to some embodiments. The photo-detectingdevice 600 a in FIG. 6A is similar to the photo-detecting device 500 ain FIG. 5A, for example, the readout electrodes 330 a, 330 b and thecontrol electrodes 340 a, 340 b are disposed at the same side of theabsorption region 10. The difference is described below.

Referring to FIG. 6A and FIG. 6B, the second doped region 108 is in thesubstrate 20. In other words, the fourth peak doping concentration ofthe second doped region 108 lies in the substrate 20. The second dopedregion 108 is below the first surface 21 of the substrate 20 and is indirect contact with the absorption region 10, for example, the seconddoped region 108 may be in contact with or overlapped with one of theside surfaces 13 of the absorption region 10. As a result, the carrierswith the second type, which are not collected by the first doped regions302 a, 302 b, can move from the absorption region 10 towards the seconddoped region 108 through the heterointerface between the absorptionregion 10 and the substrate 20. The second electrode 60 is over thefirst surface 21 of the substrate 20. The absorption region 10 isbetween the second electrode 60 and the four electrodes 330 a, 330 b,340 a, 340 b.

By having the second doped region 108 in the substrate 20 instead of inthe absorption region 10, the second electrode 60 and the fourelectrodes 330 a, 330 b, 340 a, 340 b can both be coplanarly formedabove the first surface 21 of the substrate 20. Therefore, a heightdifference between any two of the second electrode 60 and the fourelectrodes 330 a, 330 b, 340 a, 340 b can be reduced and thus thefabrication process afterwards will be benefit from this design.Besides, the area of the absorption region 10 absorbing the opticalsignal can be larger.

In some embodiments, the conducting region 201 can be overlapped withthe entire first doped regions 302 a, 302 b.

FIG. 6C illustrates a top view of a photo-detecting device, according tosome embodiments. FIG. 6D illustrates a cross-sectional view along anA-A′ line in FIG. 6C, according to some embodiments. FIG. 6E illustratesa cross-sectional view along a B-B′ line in FIG. 6C, according to someembodiments. The photo-detecting device 600 c in FIG. 6C is similar tothe photo-detecting device 600 a in FIG. 6A, the difference is describedbelow. The photo-detecting device 600 c further includes a confinedregion 180 between the absorption region 10 and the first doped regions302 a, 302 b to cover at least a part of the heterointerface between theabsorption region 10 and the substrate 20. The confined region 180 has aconductivity type different from the conductivity type of the firstdoped regions 302 a, 302 b. In some embodiments, the confined region 180includes a dopant having a peak doping concentration. The peak dopingconcentration is equal to or greater than 1×10¹⁶ cm³. The conductingregion 201 has a channel 181 formed through the confined region 180, soas to keep a part of the conducting region 201 in direct contact withthe absorption region 10 for allowing photo-carriers to move from theabsorption region 10 towards the first doped regions 302 a, 302 b. Thatis, the channel 181 is not covered by the confined region 180. In someembodiments, the peak doping concentration of the confined region 180 islower than the second peak doping concentration of the conducting region201. In some embodiments, the peak doping concentration of the confinedregion 180 is higher than the second peak doping concentration of theconducting region 201. For example, when the photo-detecting device isconfigured to collect electrons, the confined region 180 is of p-type,and the first doped regions 302 a, 302 b are of n-type. After thephoto-carriers are generated from the absorption region 10, the holeswill be evacuated through the second doped region 108 and the secondelectrode 60, and the electrons will be confined by the confined region180 and move from the absorption region 10 towards one of the firstdoped regions 302 a, 302 b through the channel 181 instead of moving outfrom the whole heterointerface between the absorption region 10 and thesubstrate 20. Accordingly, the photo-detecting device 600 c can haveimproved demodulation contrast by including the confined region 180between the absorption region 10 and the first doped regions 302 a, 302b.

FIG. 6F illustrates a top view of a photo-detecting device, according tosome embodiments. The photo-detecting device 600 f in FIG. 6F is similarto the photo-detecting device 600 c in FIG. 6C. The difference is thatthe confined region 180 is extended to cover two other side surfaces 13of the absorption region 10 to further confine the carriers to passthrough the channel 181 at one of the side surfaces 13 of the absorptionregion 10 instead of moving out from other side surfaces 13 of theabsorption region 10. In some embodiments, the peak doping concentrationof the confined region 180 is lower than the peak doping concentrationof the second doped region 108. In some embodiments, the confined region180 and the second doped region 108 are formed by two differentfabrication process steps, such as using different masks.

FIG. 6G illustrates a top view of a photo-detecting device, according tosome embodiments. The photo-detecting device 600 g in FIG. 6G is similarto the photo-detecting device 600 f in FIG. 6F. The difference is thesecond doped region 108 may function as the confined region 180described in FIG. 6F. In other words, the second doped region 108 canboth evacuate the carriers not collected by the first doped regions 302a, 302 b and confine the carriers to be collected from the absorptionregion 10 towards one of the first doped regions 302 a, 302 b throughthe channel 181 at one of the side surfaces 13 instead of moving outfrom other side surfaces 13 of the absorption region 10.

FIG. 7A illustrates a top view of a photo-detecting device, according tosome embodiments. FIG. 7B illustrates a cross-sectional view along anA-A′ line in FIG. 7A, according to some embodiments. The photo-detectingdevice 700 a is similar to the photo-detecting device 300 a in FIG. 3A.The difference is described below. In some embodiments, thephoto-detecting device includes N switches electrically coupled to theabsorption region 10 and partially formed in the substrate 20, where Nis a positive integer and is ≥3. For example, N may be 3, 4, 5, etc. Insome embodiments, the pixel of the photo-detecting apparatus furtherincludes Y control signals different from each other, wherein 3≤Y≤N andY is a positive integer, each of the control signal controls one or moreof the control regions of the photo-detecting device 700 a. In someembodiments, each of the control signals includes a phase, where thephase of one of the control signals is not overlapped with the phase ofanother control signal of the control signals. Referring to FIGS. 7A and7B, in some embodiments, the photo-detecting device 700 a includes fourswitches (not labeled) electrically coupled to the absorption region 10and partially formed in the substrate 20. Each of the switches includesa control region C1, C2, C3, C4 including a control electrode 340 a, 340b, 340 c, 340 d. Each of the switches further includes a readoutelectrode 330 a, 330 b, 330 c, 330 d separated from the controlelectrode 340 a, 340 b, 340 c, 340 d. In some embodiments, the readoutelectrodes 330 a, 330 b, 330 c, 330 d and the control electrodes 340 a,340 b, 340 c, 340 d are formed over a first surface 21 of the substrate20 and are separated from the absorption region 10.

In some embodiments, the four switches are disposed at four sidesurfaces 13 respectively.

In some embodiments, each of the switched includes a first doped region(not shown) under the readout electrodes 330 a, 330 b, 330 c, 330 d, thefirst doped regions are similar to the first doped region 302 a, 302 bas described in FIG. 3A.

In some embodiments, the pixel of the photo-detecting apparatus includesfour control signals for controlling the control regions C1, C2, C3, C4respectively so as to control the moving direction of the electrons orholes generated by the absorption region 10. For example, when voltagesare used, if the control signal controlling the control region C1 isbiased against other control signals, an electric field is createdbetween the four portions right under the control electrodes 340 a, 340b, 340 c, 340 d as well as in the absorption region 10, and freecarriers in the absorption region 10 drift towards one of the firstdoped regions under the readout electrodes 330 a, 330 b, 330 c, 330 ddepending on the direction of the electric field. In some embodiments,each of the control signals has a phase not overlapped by the phase ofone another.

In some embodiments, the conducting region 201 can be in any suitableshape, such as rectangle or square.

FIG. 7C illustrates a top view of a photo-detecting device, according tosome embodiments. The photo-detecting device 700 c is similar to thephoto-detecting device 700 a in FIG. 7A. The difference is describedbelow. The arrangements of the readout electrodes 330 a, 330 b, 330 c,330 d and the control electrodes 340 a, 340 b, 340 c, 340 d aredifferent. For example, the four switches are disposed at the fourcorners of the absorption region 10 respectively.

FIG. 7D illustrates a top view of a photo-detecting device, according tosome embodiments. The photo-detecting device 700 d is similar to thephoto-detecting device 700 a in FIG. 7A. The difference is describedbelow. The photo-detecting device 700 d includes eight switches (notlabeled) electrically coupled to the absorption region 10 and partiallyformed in the substrate 20. Similarly, each of the switches includes acontrol region (not labeled) including a control electrode 340 a, 340 b,340 c, 340 d, 340 e, 340 f, 340 g, 340 h and includes a readoutelectrode 330 a, 330 b, 330 c, 330 d, 330 e, 330 f, 330 g, 330 hseparated from the control electrode 340 a, 340 b, 340 c, 340 d, 340 e,340 f, 340 g, 340 h.

In some embodiments, a photo-detecting apparatus includes a pixelincluding the photo-detecting device 700 d as mentioned above, and thepixel includes multiple control signals different from each other andcontrolling multiple switches of the photo-detecting device 700 d. Thatis, in a same pixel, a number of the control signals is less than anumber of the switches. For example, the pixel may include two controlsignals different from each other and each of the control signalcontrols two of the switches. For example, the control electrode 340 aand the control electrode 340 c may be electrically coupled to andcontrolled by the same control signal. In some embodiments, the pixelmay include multiple control signals controlling respective switch. Thatis, in a same pixel, a number of the control signals is equal to anumber of the switches. For example, the pixel of the photo-detectingapparatus includes eight control signals different from each other andcontrolling respective switches of the photo-detecting device 700 d.

FIG. 7E illustrates a top view of a photo-detecting device, according tosome embodiments. The photo-detecting device 700 e is similar to thephoto-detecting device 700 d in FIG. 7D. The difference is describedbelow. The arrangements of the readout electrodes 330 a, 330 b, 330 c,330 d, 330 e, 330 f, 330 g, 330 h and the control electrodes 340 a, 340b, 340 c, 340 d, 340 e, 340 f, 340 g, 340 h are different. For example,every two switches of the eight switches are disposed at the fourcorners of the absorption region 10 respectively. The conducting region201 can be, but not limited to octagon.

FIG. 8A illustrates a top view of a photo-detecting device, according tosome embodiments. FIG. 8B illustrates a cross-sectional view along anA-A′ line in FIG. 8A, according to some embodiments. The photo-detectingdevice 800 a in FIG. 8A is similar to the photo-detecting device 700 ain FIG. 7A. The difference is described below. The second doped region108 is in the substrate 20. In other words, the fourth peak dopingconcentration of the second doped region 108 lies in the substrate 20.In some embodiments, the second doped region 108 includes multiplesubregions 108 a, 108 b, 108 c, 108 d separated from one another and arein direct contact with the absorption region 10, for example, thesubregions 108 a, 108 b, 108 c, 108 d may be in contact with oroverlapped with at least a part of the side surfaces 13 of theabsorption region 10. As a result, the carriers generated from theabsorption region 10 and are not collected by the first doped regionscan move from the absorption region 10 towards one or more of thesubregions 108 a, 108 b, 108 c, 108 d through the heterointerfacebetween the absorption region 10 and the substrate 20. In someembodiments, the subregions 108 a, 108 b, 108 c, 108 d are not betweenthe absorption region 10 and the first doped region of any switches toavoid blocking the path of the carriers to be collected from moving fromthe absorption region 10 towards one of the first doped regions. Forexample, in some embodiments, the subregions 108 a, 108 b, 108 c, 108 dare disposed at the four corners of the absorption region 10respectively, and the four switches are disposed at the four sidesurfaces 13 respectively, such that the path of the holes moving fromthe absorption region 10 towards one or more of the subregions 108 a,108 b, 108 c, 108 d and the path of the electrons moving from theabsorption region 10 towards one of the first doped regions aredifferent.

In some embodiment, the second electrode 60 includes sub-electrodes 60a, 60 b, 60 c, 60 d electrically coupled to the subregions 108 a, 108 b,108 c, 108 d respectively. The sub-electrodes 60 a, 60 b, 60 c, 60 d aredisposed over the first surface 21 of the substrate 20.

By having the second doped region 108 in the substrate 20 instead of inthe absorption region 10, the sub-electrodes 60 a, 60 b, 60 c, 60 d, thereadout electrodes 330 a, 330 b, 330 c, 330 d, and the controlelectrodes 340 a, 340 b, 340 c, 340 d, can all be coplanarly formedabove the first surface 21 of the substrate 20. Therefore, a heightdifference between any two of the sub-electrodes 60 a, 60 b, 60 c, 60 d,the readout electrodes 330 a, 330 b, 330 c, 330 d, and the controlelectrodes 340 a, 340 b, 340 c, 340 d can be reduced and thus thefabrication process afterwards will be benefit from this design.Besides, the area of the absorption region 10 absorbing the opticalsignal can be larger.

FIG. 8C illustrates a top view of a photo-detecting device, according tosome embodiments. The photo-detecting device 800 c in FIG. 8C is similarto the photo-detecting device 800 a in FIG. 8A. The difference isdescribed below. The arrangements of the readout electrodes 330 a, 330b, 330 c, 330 d and the control electrodes 340 a, 340 b, 340 c, 340 dare different, the arrangement of the sub-electrodes 60 a, 60 b, 60 c,60 d is different, and the arrangement of the subregions 108 a, 108 b,108 c, 108 d is different. For example, the four switches are disposedat the four corners of the absorption region 10 respectively, and thesubregions 108 a, 108 b, 108 c, 108 d and the sub-electrodes 60 a, 60 b,60 c, 60 d are disposed at respective side surfaces 13 of the absorptionregion 10.

FIG. 8D illustrates a top view of a photo-detecting device, according tosome embodiments. The photo-detecting device 800 d is similar to thephoto-detecting device 800 a in FIG. 8A. The difference is describedbelow. The photo-detecting device 800 d includes eight switches (notlabeled) electrically coupled to the absorption region 10 and partiallyformed in the substrate 20, which are similar to the photo-detectingdevice 700 d in FIG. 7D. The pixel of the photo-detecting apparatus alsoincludes multiple control signals as described in FIG. 7D.

FIG. 8E illustrates a top view of a photo-detecting device, according tosome embodiments. The photo-detecting device 800 e is similar to thephoto-detecting device 800 d in FIG. 8D. The difference is describedbelow. The arrangements of the readout electrodes 330 a, 330 b, 330 c,330 d 330 e, 330 f, 330 g, 330 h and the control electrodes 340 a, 340b, 340 c, 340 d, 340 e, 340 f, 340 g, 340 h are different, thearrangement of the sub-electrodes 60 a, 60 b, 60 c, 60 d is different,and the arrangement of the subregions 108 a, 108 b, 108 c, 108 d isdifferent. For example, every two switches of the eight switches aredisposed at the four corners of the absorption region 10 respectively,and the subregions 108 a, 108 b, 108 c, 108 d and the sub-electrodes 60a, 60 b, 60 c, 60 d are disposed at respective side surfaces 13 of theabsorption region 10.

FIG. 9A shows a schematic diagram of a photo-detecting apparatus,according to some embodiments. The photo-detecting apparatus 900 aincludes a pixel (not labeled) and a column bus electrically coupled tothe pixel. The pixel includes a photo-detecting device and multiplereadout circuits (not labeled) electrically coupled to thephoto-detecting device and the column bus. The photo-detecting devicecan be any photo-detecting device as described in FIG. 0.3A through FIG.3B, FIG. 4A through FIG. 4C, FIG. 5A through FIG. 5C, FIG. 0.6A throughFIG. 6G, FIG. 7A through FIG. 7E, and FIG. 8A through FIG. 8E. Forexample, the photo-detecting device 300 a in FIG. 3B is illustrated inFIG. 9A. Each of the readout circuits is similar to the readout circuitas described in FIG. 2E. The difference is described below. Each of thereadout circuits is electrically coupled to the respective first dopedregion of the switches of the photo-detecting device for processing thecarriers of the first type. For example, if the first doped region is ofn-type, the readout circuits process the electrons collected fromrespective first doped region for further application.

The number of the readout circuits is the same as the number ofswitches. That is, the photo-detecting device includes N switcheselectrically coupled to the absorption region 10 and partially formed inthe substrate 20, and the pixel of the photo-detecting apparatus furtherincludes Z readout circuits electrically coupled to the photo-detectingdevice, where Z=N. For example, the number of the switches of thephoto-detecting device in FIG. 3A through FIG. 3B, FIG. 4A through FIG.4C, FIG. 5A through FIG. 5C, FIG. 6A through FIG. 6G is two, and thenumber of the readout circuits is two. For another example, the numberof the switches of the photo-detecting device in FIG. 7A through FIG.7C, and FIG. 8A through FIG. 8C is four, and the number of the readoutcircuits is four. For another example, the number of the switches of thephoto-detecting device in FIG. 7D through FIG. 7E, and FIG. 8D throughFIG. 8E is eight, and the number of the readout circuits is eight.

FIG. 9B shows a schematic diagram of a photo-detecting apparatus,according to some embodiments. The photo-detecting apparatus 900 b issimilar to the photo-detecting apparatus 900 a in FIG. 9A. Thedifference is described below. Similar to the readout circuit asdescribed in FIG. 2F, the readout circuit of the photo-detectingapparatus 900 b further includes a voltage-control transistor 130Abetween the first/second switch of the photo-detecting device 300 a andthe capacitor 150A.

FIG. 10A illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device includes anabsorption region 10 and a substrate 20 supporting the absorption region10. The absorption region 10 is similar to the absorption region 10 asdescribed in FIG. 1A. The substrate 20 is similar to the substrate 20 asdescribed in FIG. 1A. The difference between the photo-detecting device1000 a in FIG. 10A and the photo-detecting device 100 a in FIG. 1A isdescribed below. In some embodiments, the photo-detecting device 1000 afurther includes a first contact region 204 separated from theabsorption region 10 and in the substrate 20. The photo-detecting device1000 a further includes a second contact region 103 in the absorptionregion 10.

In some embodiments, the second contact region 103 is of a conductivitytype. The first contact region 204 is of a conductivity type differentfrom the conductivity type of the second contact region 103. In someembodiments, the second contact region 103 includes a dopant having apeak doping concentration higher than the first peak dopingconcentration of the absorption region 10, for example, can be rangingfrom 1×10¹⁸ cm⁻³ and 5×10²⁰ cm⁻³. In some embodiments, the first contactregion 204 includes a dopant having a peak doping concentration higherthan the second peak doping concentration of the second dopant of thesubstrate 20, for example, can be ranging from 1×10¹⁸ cm⁻³ and 5×10²⁰cm³. In some embodiments, the second contact region 103 is not arrangedover the first contact region 204 along the direction D1 substantiallyvertical to the first surface 21 of the substrate 20.

The photo-detecting device includes a first electrode 140 coupled to thefirst contact region 204 and a second electrode 160 coupled to thesecond contact region 103. The second electrode 160 is over the firstsurface 11 of the absorption region 10. The first electrode 140 is overthe first surface 21 of the substrate 20. In some embodiments, thesubstrate 20 of the photo-detecting device 1000 a includes a conductingregion 201 similar to the conducting region 201 as described in FIG. 1A.

In some embodiments, the photo-detecting device 1000 a further includesa third contact region 208 in the substrate 20. In some embodiments, thethird contact region 208 is between the second contact region 103 andthe first contact region 204. The third contact region 208 is of aconductivity type the same as the conductivity type of the secondcontact region 103. The third contact region 208 includes a conductivitytype different from the conductivity type of the first contact region204. In some embodiments, the third contact region 208 includes a dopanthaving a peak doping concentration higher than the second peak dopingconcentration of the conducting region 201, for example, can be between1×10¹⁸ cm³ and 5×10²⁰ cm³.

In some embodiments a distance between the first surface 21 of thesubstrate 20 and a location of the first contact region 204 having thepeak dopant concentration is less than 30 nm. In some embodiments adistance between the first surface 21 of the substrate 20 and a locationof the third contact region 208 having the peak dopant concentration isless than 30 nm.

In some embodiments, the third contact region 208 may be entirelyoverlapped with the conducting region 201. The third contact region 208and the first contact region 204 are both beneath the first surface 21of the substrate 20.

In some embodiments, the photo-detecting device further includes a thirdelectrode 130 electrically coupled to the third contact region 208. Thethird electrode 130 and the first electrode 140 are coplanarly formed onthe first surface 21 of the substrate 20, and thus a height differencebetween the third electrode 130 and the first electrode 140 can bereduced, which benefits the fabrication process afterwards

The photo-detecting device 1000 a can be a lock-in pixel or an avalanchephototransistor depending on the circuits electrically coupled to thephoto-detecting device 1000 a and/or the operating method of thephoto-detecting device 1000 a.

For example, if the photo-detecting device 1000 a serves as a lock-inpixel, the third contact region 208 and the first contact region 204 canbe regarded as a switch. A readout circuit is electrically coupled tothe first contact region 204 through the first electrode 140, a controlsignal, which is a modulated signal, is electrically coupled to thethird contact region 208 through the third electrode 130 for controllingthe on and off state of the switch, and a voltage or ground may beapplied to the second contact region 103 for evacuating the carriers notcollected by the first contact region 204. The lock-in pixel can beincluded in an indirect TOF system.

In some embodiments, if the photo-detecting device 1000 a serves as anavalanche phototransistor, the part of the substrate 20 or the part ofthe conducting region 201 between the third contact region 208 and thefirst contact region 204, where the carriers pass through, serves as amultiplication region M during the operation of the photo-detectingdevice 1000 a. In the multiplication region, photo-carriers generateadditional electrons and holes through impact ionization, which startsthe chain reaction of avalanche multiplication. As a result, thephoto-detecting device 1000 a has a gain. In some embodiments, thesubstrate 20 supports the absorption region 10 and is capable ofamplifying the carriers by avalanche multiplication at the same time.

In some embodiments, the third contact region 208 may be a chargeregion. The avalanche phototransistor can be included in a direct TOFsystem.

A method for operating the photo-detecting device 1000 a capable ofcollecting electrons in FIG. 10A, includes steps of, applying a firstvoltage to a first electrode 140, applying a second voltage to thesecond electrode 160, and applying a third voltage to a third electrode130 to generate a first total current and form a reverse-biased p-njunction between the first electrode 140 and the third electrode 130;and receiving an incident light in the absorption region 10 to generatea second total current, where the second total current is larger thanthe first total current.

In some embodiments, the first voltage is greater than the secondvoltage. In some embodiments, the third voltage is between the firstvoltage and the second voltage.

In some embodiments, the first total current includes a first currentand a second current. The first current flows from the first electrode140 to the third electrode 130. The second current flows from the firstelectrode 140 to the second electrode 160.

In some embodiments, the second total current includes a third current.The third current flows from the first electrode 140 to the secondelectrode 160.

In some embodiments, the second total current includes the third currentand a fourth current. The fourth current flows from the first electrode140 to the third electrode 130.

In some embodiments, the second voltage applied to the first electrodeis, for example, 0 Volts.

In some embodiments, the third voltage can be selected to sweep thephoto-carriers from the absorption region 10 to the multiplicationregion, that is, the part of the substrate 20 or the part of theconducting region 201 between the third contact region 208 and the firstcontact region 204. In some embodiments, a voltage difference betweenthe second voltage and third voltage is less than a voltage differencebetween the first voltage and the third voltage to facilitate themovement of photo-carriers from absorption region 10 to themultiplication region in the substrate 20 so as to multiply thephoto-carriers. For example, when the second voltage applied to thesecond electrode 160 is 0 Volts, a third voltage applied to the thirdelectrode 130 is 1V, and the first voltage applied to the firstelectrode 140 can be 7V.

In some embodiments, a voltage difference between the first voltage andthe third voltage is less than an avalanche breakdown voltage of thephoto-detecting device 1000 a, at which the photo-detecting device 1000a initiates the chain reaction of avalanche multiplication, to operatethe multiplication region in a linear mode.

In some embodiments, a voltage difference between the first voltage andthe third voltage is higher than an avalanche breakdown voltage of thephoto-detecting device 1000 a, at which the photo-detecting device 1000a initiates the chain reaction of avalanche multiplication, to operatethe multiplication region in a Geiger mode.

In some embodiments, the carriers collected by the first contact region204 can be further processed by a circuit electrically coupled to thephoto-detecting device 1000 a.

In some embodiments, the carriers not collected by the first contactregion 204 can move towards the second contact region 103 and can befurther evacuated by a circuit electrically coupled to thephoto-detecting device 1000 a.

Similarly, by the design of the concentration and the material of theabsorption region 10 and the carrier conducting layer, that is thesubstrate 20 in some embodiments, the photo-detecting device 1000 a canhave lower dark current.

FIG. 10B illustrates a top view of a photo-detecting device, accordingto some embodiments. FIG. 10C illustrates a cross-sectional view alongan A-A′ line in FIG. 10B, according to some embodiments. Thephoto-detecting device 1000 b in FIG. 10B is similar to thephoto-detecting device 1000 a in FIG. 10A. The difference is describedbelow. Preferably, the photo-detecting device 1000 b serves as anavalanche phototransistor. The photo-detecting device 1000 b furtherincludes a modification element 203 integrated with the substrate 20.The modification element 203 is for modifying the position where themultiplication occurs in the substrate 20. In some embodiments, theresistivity of the modification element 203 is higher than theresistivity of the substrate 20 so as to modify the position where themultiplication occurs in the substrate 20. Accordingly, more carrierscan pass through the place where the strongest electric field locates,which increases the avalanche multiplication gain.

For example, the modification element 203 is a trench formed in thefirst surface 21 of the substrate 20. The trench can block the carriersfrom passing through a defined region of the substrate 20, and thusreduces the area in the substrate 20 where the carriers pass through.The trench has a depth, and a ratio of the depth to the thickness of thesubstrate 20 can be between 10% and 90%. The first contact region 204 isexposed in the trench to be electrically coupled to the first electrode140. In some embodiments, a width of the trench can be greater than,substantially equal or less than a width of the first contact region204. In some embodiments, a width of the trench can be greater than awidth of the first contact region 204 so as to enforce carriers passingthrough the high-field region next to the first contact region 204.

By the modification element 203, the carriers, for example, electrons,are forced to pass through the multiplication region, where thestrongest electric field locates, such as the region next to the firstcontact region 204, which increases the avalanche multiplication gain.

In some embodiments, the first electrode 140 is formed in the trench. Aheight difference is between the third electrode 130 and the firstelectrode 140.

In some embodiments, the conducting region 201 may be separated from thethird contact region 208, overlapped with a part of the third contactregion 208, overlapped with the entire third contact region 208, touchesthe corner of the trench, or partially overlapped with the first contactregion 204.

In some embodiment, an insulating material may be filled in the trench.

FIG. 10D illustrates a top view of a photo-detecting device, accordingto some embodiments. FIG. 10E illustrates a cross-sectional view alongan A-A′ line in FIG. 10D, according to some embodiments. FIG. 10Fillustrates a cross-sectional view along a B-B′ line in FIG. 10D,according to some embodiments. The photo-detecting device 1000 d in FIG.10D is similar to the photo-detecting device 1000 b in FIG. 10B. Thedifference is described below. In some embodiments a distance betweenthe first surface 21 of the substrate 20 and a location of the thirdcontact region 208 having the peak dopant concentration is greater than30 nm. In some embodiments, the photo-detecting device 1000 d furtherincludes a recess 205 formed in the first surface 21 of the substrate 20and exposing the third contact region 208. The third electrode 130 isformed in the recess 205 to be electrically coupled to the third contactregion 208. Since the distance between the first surface 21 of thesubstrate 20 and a location of the third contact region 208 having thepeak dopant concentration is greater than 30 nm, a distance between thethird contact region 208 and the first contact region 204 is shorter,which further confines the traveling path of the carriers so as to forcemore carriers passing through the place where the strongest electricfield locates. Accordingly, the avalanche multiplication gain is furtherimproved. In some embodiments, an insulating material may be filled inthe recess 205. The first electrode may include interconnects or plugs.

FIG. 10G illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 1000 g in FIG.10G is similar to the photo-detecting device 1000 d in FIG. 10D. Thedifference is described below. In some embodiments, the photo-detectingdevice 1000 g includes multiple third contact regions 208 and multiplefirst contact regions 204. The third contact regions 208 and multiplefirst contact regions 204 are in a staggered arrangement. By thisdesign, multiple multiplication regions can be formed between themultiple third contact regions 208 and multiple first contact regions204, providing a more uniform electric field profile compared to thephoto-detecting device 1000 d. In addition, the carriers mainly driftalong the direction D1 substantially vertical to the first surface 21 ofthe substrate 20, which increases the speed of the photo-detectingdevice 1000 g because the vertical transit distance is usually shorter.

In some embodiments, the second contact region 103 is arranged over thefirst contact regions 204 along the direction D1 substantially verticalto the first surface 21 of the substrate 20. In some embodiments, amaximum distance d2 between two outermost third contact regions 208 isgreater than a width w3 of the conducting region 201, which forcescarriers generated from the absorption region 10 passing through themultiple multiplication regions between the multiple third contactregions 208 and multiple first contact regions 204 instead of movinginto other undesired region in the substrate 20.

In some embodiments, the multiple third contact regions 208 may beseparated from one another. In some embodiments, the multiple firstcontact regions 204 may be separated from one another. In someembodiments, the multiple third contact regions 208 may be a continuousregion. In some embodiments, the multiple first contact regions 204 maybe a continuous region.

In some embodiments, the first contact regions 204 may be in aninterdigitated arrangement from a top view of a first plane (not shown).In some embodiments, the third contact regions 208 may be in aninterdigitated arrangement from a top view of a second plane (not shown)different form the first plane.

In some embodiments, one or more third electrodes 130 can beelectrically coupled to the third contact regions 208 through anysuitable structures, such as vias, from another cross-sectional view ofthe photo-detecting device 1000 g taken along from another plane. Insome embodiments, one or more first electrodes 140 can be electricallycoupled to the first contact regions 204 through any suitablestructures, such as vias, from another cross-sectional view of thephoto-detecting device 1000 g taken along from another plane.

FIG. 10H illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 1000 h in FIG.10H is similar to the photo-detecting device 1000 a in FIG. 10A. Thedifference is described below.

The photo-detecting device 1000 h further includes a middle-doped region210 in the substrate 20 and may partially overlapped with the conductingregion 201. The middle-doped region 210 is of a conductivity type thesame as the conductivity type of the third contact region 208. Themiddle-doped region 210 includes a dopant having a peak dopingconcentration lower than peak doping concentration of the third contactregion 208, for example, can be between 1×10¹⁶ cm⁻³ and 1×10¹⁸ cm³.

The photo-detecting device 1000 h further includes a lower-doped region212 in the substrate 20. The lower-doped region 212 is of a conductivitytype the same as the conductivity type of the first contact region 204.The lower-doped region 212 includes a dopant having a peak dopingconcentration lower than peak doping concentration of the first contactregion 204, for example, can be between 1×10¹⁸ cm³ and 1×10²⁰ cm³.

The middle-doped region 210 is between the lower-doped region 212 andthe second contact region 103 along a direction substantially verticalto the first surface 21 of the substrate 20. In some embodiments, aposition where the peak doping concentration of the lower-doped region212 locates is deeper than the position where the peak dopingconcentration of the middle-doped region 210 locates.

In some embodiments, the depth of the third contact region 208 is lessthan the depth of the first contact region 204. The depth is measuredfrom the first surface 21 of the substrate 20 along a directionsubstantially perpendicular to the first surface 21 of the substrate 20.The depth is to a position where the dopant profile of the dopantreaches a certain concentration, such as 1×10¹⁵ cm⁻³.

A multiplication region M can be formed between the lower-doped region212 and the middle-doped region 210 during the operation of thephoto-detecting device 1000 h. The multiplication region M is configuredto receive the one or more charge carriers from the middle-doped region210 and generate one or more additional charge carriers. Themultiplication region M has a thickness that is normal to the firstsurface 21 and that is sufficient for the generation of one or moreadditional charge carriers from the one or more carriers that aregenerated in the absorption region 10. The thickness of themultiplication region M can range, for example, between 100-500nanometers (nm). The thickness may determine the voltage drop of themultiplication region M to reach avalanche breakdown. For example, athickness of 100 nm corresponds to about 5-6 Volts voltage drop requiredto achieve avalanche breakdown in the multiplication region M. Inanother example, a thickness of 300 nm corresponds to about 13-14 Voltsvoltage drop required to achieve avalanche breakdown in themultiplication region M.

In some embodiments, the shape of the third contact region 208, theshape of the first contact region 204, the shape of the third electrode130, and the shape of the first electrode 140 may be but not limited toa ring.

Compared to the photo-detecting device 1000 c in FIG. 10C, themultiplication region M in the photo-detecting device 1000 h can beformed in the bulk area of the substrate 20, which avoids defects thatmay present at the trench surface described in FIG. 10C. As a result,the dark current is further reduced. Furthermore, a height differencebetween the third electrode 130 and the first electrode 140 can bereduced and thus the fabrication process afterwards will be benefit fromthis design.

FIG. 10I illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 1000 i in FIG.10I is similar to the photo-detecting device 1000 h in FIG. 10H. Thedifference is described below. The substrate 20 includes a base portion20 a, an upper portion 20 b and a middle portion 20 c. The middleportion 20 c is between the base portion 20 a and the upper portion 20b. The absorption region 10, the second contact region 103 and theconducting region 201 are in the upper portion 20 b. The third contactregion 208 is in the middle portion 20 c. The first contact region 204is in the base portion 20 a. The upper portion 20 b has a width lessthan a width of the middle portion 20 c, and the third contact region208 is exposed to be electrically coupled to the third electrode 130.The middle portion 20 c has a width less than a width of the baseportion 20 a, and the first contact region 204 is exposed to beelectrically coupled to the first electrode 140.

The middle-doped region 210 is in the middle portion 20 c. Thelower-doped region 212 is in the base portion 20 a. Compared to thephoto-detecting device 1000 c in FIG. 10C, the multiplication region Min the photo-detecting device 1000 h can be formed in the bulk area ofthe middle portion 20 c, which avoids defects that may present at thetrench surface described in FIG. 10C. As a result, the dark current isfurther reduced.

FIG. 11A illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 1100 a in FIG.11A is similar to the photo-detecting device 1000 a in FIG. 10A. Thedifference is described below.

The second contact region 103 is in the substrate 20. In other words,the peak doping concentration of the second contact region 103 lies inthe substrate 20. In some embodiment, the second contact region 103 isbelow the first surface 21 of the substrate 20 and is in direct contactwith the absorption region 10, for example, the second contact region103 may be in contact with or overlapped with one of the side surfaces13 of the absorption region 10 that is opposite to the third contactregion 208 and/or the first contact region 204. As a result, thecarriers generated from the absorption region 10 can move from theabsorption region 10 towards the second contact region 103 through theheterointerface between the absorption region 10 and the substrate 20.The second electrode 160 is over the first surface 21 of the substrate20.

By having the second contact region 103 in the substrate 20 instead ofin the absorption region 10, the second electrode 160, the firstelectrode 140 and the third electrode 130 can all be coplanarly formedabove the first surface 21 of the substrate 20. Therefore, a heightdifference between the any two of the second electrode 160, the thirdelectrode 130 and the first electrode 140 can be reduced and thus thefabrication process afterwards will be benefit from this design.Besides, the area of the absorption region 10 absorbing the opticalsignal can be larger.

FIG. 11B illustrates a top view of a photo-detecting device, accordingto some embodiments. FIG. 11C illustrates a cross-sectional view alongan A-A′ line in FIG. 11B, according to some embodiments. Thephoto-detecting device 1100 b in FIG. 11B is similar to thephoto-detecting device 1100 a in FIG. 11A. The difference is describedbelow. The photo-detecting device 1100 b further includes a modificationelement 203 integrated with the substrate 20. The modification element203 is similar to the modification element 203 as described in FIGS. 10B and 10C.

FIG. 11D illustrates a top view of a photo-detecting device, accordingto some embodiments. FIG. 11E illustrates a cross-sectional view alongan A-A′ line in FIG. 11D, according to some embodiments. Across-sectional view along a B-B′ line in FIG. 11D is the same as FIG.10F. The photo-detecting device 1100 d in FIG. 11D is similar to thephoto-detecting device 1100 b in FIG. 11B. The difference is describedbelow. The third contact region 208 is similar to the third contactregion 208 in FIG. 10D and FIG. 10E. Besides, the photo-detecting device1100 d further includes a recess 205 similar to the recess 205 asdescribed in FIG. 10D and FIG. 10F, and the third electrode 130 isformed in the recess 205 to be electrically coupled to the third contactregion 208.

FIG. 12A illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 1200 a in FIG.12A is similar to the photo-detecting device 1000 c in FIG. 10C. Thedifference is described below. From the cross-sectional view of aphoto-detecting device, the photo-detecting device 1200 a includes twothird contact regions 208, two first contact regions 204, two thirdelectrodes 130 and two first electrodes 140. The third contact regions208 are disposed at two opposite sides of the absorption region 10, andthe two third electrodes 130 are electrically coupled to the respectivethird contact region 208. The first contact regions 204 are disposed attwo opposite sides of the absorption region 10, and the first electrodes140 are electrically coupled to the respective first contact region 204.A distance between the third contact regions 208 is less than a distancebetween the first contact regions 204. The substrate 20 further includesa waveguide 206 associated with the absorption region 10 for guidingand/or confining the incident optical signal passing through a definedregion of the substrate 20. For example, the waveguide 206 may be aridge defined by two trenches 207. The ridge is with a width greaterthan a width of the absorption region 10. An incident optical signal canbe confined and propagate along the ridge 206. The trench may be similarto the trench mentioned in FIG. 10B and FIG. 10C, and may also be amodification element 203 as mentioned in FIG. 10B and FIG. 10C. Forexample, carriers are forced to pass through the multiplication regionwhere the strongest electric field locates, such as the region near thecorner of each of the trenches, which increases the avalanchemultiplication gain. Similar to FIG. 10B and FIG. 10C, each of the firstcontact regions 204 is exposed in the respective trench 207 forelectrically coupled to the respective first electrode 140.

FIG. 12B illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 1200 b in FIG.12B is similar to the photo-detecting device 1100 a in FIG. 12A. Thedifference is described below. The third contact regions 208 are similarto the third contact region 208 in FIG. 10 D and FIG. 10E. For example,a distance between the first surface 21 of the substrate 20 and alocation of each of the third contact regions 208 having the peak dopantconcentration is greater than 30 nm.

FIG. 12C illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 1200 c in FIG.12C is similar to the photo-detecting device 1000 g in FIG. 10G. Thedifference is described below. The photo-detecting device 1200 c furtherincludes a waveguide 206 integrated with the substrate 20, where thewaveguide 206 is similar to the waveguide 206 described in FIG. 12A.

FIG. 13A illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device includes anabsorption region 10 and a substrate 20 supporting the absorption region10. The absorption region 10 is similar to the absorption region 10 asdescribed in FIG. 1A. The substrate 20 is similar to the substrate 20 asdescribed in FIG. 1A. The difference between the photo-detecting device1300 a in FIG. 13A and the photo-detecting device 100 a in FIG. 1A isdescribed below.

The photo-detecting device 1300 a includes a collector region 1302 andan emitter region 1304 separated from the collector region 1302. In someembodiments, the collector region 1302 is in the absorption region 10.The emitter region 1304 is outside of the absorption region 10 and is inthe substrate 20. The collector region 1302 is for collecting amplifiedphoto-carriers generated from the absorption region 10. The collectorregion 1302 is of a conductivity type. The emitter region 1304 is of aconductivity type the same as the conductivity type of the collectorregion 1302. The conductivity type of the absorption region 10 is thesame as the conductivity type of the collector region 1302. For example,the conductivity type of the absorption region 10 is p-type, and theconductivity type of the collector region 1302 and the conductivity typeof the emitter region 1304 are p-type. In some embodiments, thecollector region 1302 includes a dopant and has a dopant profile with apeak dopant concentration higher than the first peak dopingconcentration of the absorption region 10, for example, may be rangingfrom 5×10¹⁸ cm⁻³ to 5×10²⁰ cm⁻³.

In some embodiments, the emitter region 1304 includes a dopant and has adopant profile with a peak dopant concentration higher than the secondpeak doping concentration of the second dopant of the substrate 20, forexample, can be ranging from, 1×10¹⁷ cm⁻³ to 5×10¹⁸ cm³.

The photo-detecting device 1300 a includes a first electrode 1330electrically coupled to the collector region 1302 and includes a secondelectrode 1340 electrically coupled to the emitter region 1304. Thefirst electrode 1330 serves as a collector electrode. The secondelectrode 1340 serves as an emitter electrode.

In some embodiments, similar to the conducting area described in FIG.1A, a conducting area (not shown) can be formed in the carrierconducting layer, that is the substrate 20 in some embodiments. Theconducting region 201 is between the emitter region 1304 and theabsorption region 10. In some embodiments, the conducting region 201 ispartially overlapped with the absorption region 10 and the emitterregion 1304 for confining a path of the carriers generated from theabsorption region 10 moving towards the emitter region 1304. In someembodiments, the conducting region 201 has a depth measured from thefirst surface 21 of the substrate 20 along a direction substantiallyperpendicular to the first surface 21 of the substrate 20. The depth isto a position where the dopant profile of the second dopant reaches acertain concentration, such as 1×10¹⁵ cm⁻³.

Similarly, by the design of the concentration and the material of theabsorption region 10 and the carrier conducting layer, that is thesubstrate 20 in some embodiments, the photo-detecting device 1300 a canhave lower dark current.

In some embodiments, a method for operating the photo-detecting device1300 a includes the steps of: generating a reversed-biased PN junctionbetween the absorption region 10 and the substrate 20 and generating aforward-biased PN junction between the substrate 20 and the emitterregion 1304; and receiving an incident light in the absorption region 10to generate an amplified photo current.

For example, the photo-detecting device 1300 a may include a p-dopedemitter region 1304, a n-doped substrate 20, a p-doped absorption region10, and an p-doped collector region 1302. The PN junction between thep-doped emitter region 1304 and the n-doped substrate 20 isforward-biased such that a hole-current is emitted into the n-dopedsubstrate 20. The PN junction between the p-doped absorption region 10and the n-doped substrate 20 is reverse-biased such that the emittedhole-current is collected by the first electrode 1330. When light (e.g.,a light at 940 nm, 1310 nm, or any suitable wavelength) is incident onthe photo-detecting device 1300 a, photo-carriers including electronsand holes are generated in the absorption region 10. The photo-generatedholes are collected by the first electrode 1330. The photo-generatedelectrons are directed towards the n-doped substrate 20, which causesthe forward-bias to increase due to charge neutrality. The increasedforward-bias further increases the hole-current being collected by thefirst electrode 1330, resulting in an amplified hole-current generatedby the photo-detecting device 1300 a.

Accordingly, a second electrical signal collected by the collectorregion 1302 is greater than the first electrical signal generated by theabsorption region 10, and thus the photo-detecting device 1300 a is withgain and thus is with improved signal to noise ratio.

In some embodiments, a method for operating the photo-detecting device1300 a capable of collecting holes includes the steps of: applying afirst voltage V1 to the first electrode 1330 and applying a secondvoltage V2 to the second electrode 1340 to generate a first currentflowing from the second electrode 1340 to the first electrode 1330,where the second voltage V2 is higher than the first voltage V1; andreceiving an incident light in the absorption region 10 to generate asecond current flowing from the second electrode 1340 to the firstelectrode 1330 after the absorption region 10 generates photo-carriersfrom the incident light, where the second current is larger than thefirst current.

In some embodiments, a method for operating the photo-detecting device1300 a capable of collecting holes includes the steps of: applying asecond voltage V2 to the second electrode 1340 to form a forward-biasbetween the emitter region 1304 and the substrate 20 to form a firsthole current, and applying a first voltage to the first electrode 1330to form a reverse-bias between the substrate 20 and an absorption region10 to collect a portion of the first hole current, where the secondvoltage V2 is higher than the first voltage V1; receiving an incidentlight in the absorption region 10 to generate photo-carriers includingelectrons and holes; and amplifying a portion of the holes of thephoto-carriers to generate a second hole current; and collecting aportion of the second hole current by the collector region 1302, wherethe second hole current is larger than the first hole current.

FIG. 13B illustrates a cross-sectional view of a photo-detecting device,according to some embodiments. The photo-detecting device 1300 b in FIG.13B is similar to the photo-detecting device 1300 a in FIG. 13A. Thedifference is described below. The photo-detecting device furtherincludes a base region 1308 and a third electrode 1360 electricallycoupled to the base region 1308. The third electrode 1360 serves as abase electrode. In some embodiments, the base region 1308 is between thecollector region 1302 and the emitter region 1304. The base region 1308is of a conductivity type different from the conductivity type of thecollector region 1302. In some embodiments, base region 1308 is in thesubstrate 20.

In some embodiments, the base region 1308 includes a dopant and has adopant profile with a peak dopant concentration higher than the secondpeak doping concentration of the second dopant of the substrate 20, forexample, can be ranging from 1×10¹⁷ cm⁻³ to 5×10¹⁸ cm⁻³.

The third electrode 1360 is for biasing the base contact region 1308. Insome embodiments, the third electrode 1360 is for evacuating thephoto-carriers with opposite type and not collected by the firstelectrode 1330 during the operation of the photo-detecting device 1300b. For example, if the photo-detecting device 1300 b is configured tocollect holes, which are further processed by such as circuitry, thethird electrode 1360 is for evacuating electrons. Therefore, thephoto-detecting device 1300 b can have improved reliability.

In some embodiments, a method for operating the photo-detecting device1300 b capable of collecting holes includes the steps of: applying asecond voltage V2 to the second electrode 1340 to form a forward-biasbetween the emitter region 1304 and the substrate 20 to form a firsthole current, and applying a first voltage to the first electrode 1330to form a reverse-bias between the substrate 20 and an absorption region10 to collect a portion of the first hole current, where the secondvoltage V2 is higher than the first voltage V1; applying a third voltageto a third electrode 60 electrically coupled to a base contact region1308 of the photo-detecting device; receiving an incident light in theabsorption region 10 to generate photo-carriers including electrons andholes; and amplifying a portion of the holes of the photo-carriers togenerate a second hole current; and collecting a portion of the secondhole current by the collector region 1302, and where the third voltageV3 is between the first voltage V1 and the second voltage V2.

A reverse-biased is formed across the p-n junction between the collectorregion 1302 and the base region 1308, and a forward-biased is formedacross the p-n junction between the emitter region 1304 and the baseregion 1308. In some embodiments, where the step of the applying thethird voltage V3 to the third electrode 1360 and the step of applyingthe first voltage V1 to the first electrode 30 and applying the secondvoltage V2 to the second electrode 1340 are operated at the same time.

In some embodiments, the arrangement of the third electrode 1360, firstelectrode 1330 and the second electrode 1340 and the arrangement of thebase region 1308, collector region 1302 and the emitter region 1304 canbe different. For example, in some embodiments, the second electrode1340 is between the first electrode 1330 and the third electrode 1360.The emitter region 1304 is between the collector region 1302 and thebase region 1308.

FIG. 14A illustrates a cross-sectional view of a portion of aphoto-detecting device, according to some embodiments. Thephoto-detecting device can be any photo-detecting device describedbefore. The photo-detecting device further includes a passivation layer1400 over a first surface 11 of the absorption region 10. In someembodiments, the passivation layer 1400 further covers a portion of thefirst surface 21 of the substrate 20, and the readout electrodes 330 a,330 b and the control electrodes 340 a, 340 b may be or may not be overa first surface 1401 of the passivation layer 1400. In some embodiments,the absorption region 10 is protruded from the first surface 21 of thesubstrate 20, and the passivation layer 1400 further covers sidesurfaces 13 of the absorption region 10 exposed from the substrate 20.That is, the passivation layer 1400 may be conformally formed on theabsorption region 10 and the substrate 20 as shown in FIG. 14B. In someembodiments, the second electrode 60 is formed on a surface of thepassivation layer 1400 higher than a surface of the passivation layer1400 where the readout electrodes 330 a, 330 b and the controlelectrodes 340 a, 340 b may be formed. In some embodiments, the controlelectrodes 340 a, 340 b, the readout electrodes 330 a, 330 b and thesecond electrode 60 are all disposed over the of the first surface ofthe carrier conducting layer. That is, the control electrodes 340 a, 340b, the readout electrodes 330 a, 330 b and the second electrode 60 areover a same side of the carrier conducting layer, that is thepassivation layer 1400 in some embodiments, which is benefit for thebackend fabrication process afterwards.

The passivation layer 1400 may include amorphous silicon, poly silicon,epitaxial silicon, aluminum oxide (e.g., Al_(x)O_(y)), silicon oxide(e.g., Si_(x)O_(y)), Ge oxide (e.g., Ge_(x)O_(y)), germanium-silicon(e.g., GeSi), silicon nitride family (e.g., Si_(x)N_(y)), high-kmaterials (e.g. HfO_(x), ZnO_(x), LaO_(x), LaSiO_(x)), and anycombination thereof. The presence of the passivation layer 1400 may havevarious effects. For example, the passivation layer 1400 may act as asurface passivation layer to the absorption region 10, which may reducedark current or leakage current generated by defects occurred at theexposed surface of the absorption region 10. In some embodiments, thepassivation layer 1400 may have a thickness between 20 nm and 100 nm.FIG. 14B illustrates a cross-sectional view along a line passing throughsecond doped region 108 of the photo-detecting device, according to someembodiments. In some embodiments, a part of the doped region in theabsorption region 10, such as second doped region 108 or the secondcontact region 103 may be formed in the corresponding portions of thepassivation layer 1400. That is, the dopant of the doped region, such asthe second doped region 108 or the second contact region 103, may be inthe corresponding portions of the passivation layer 1400 between theabsorption region 10 and the respective electrode.

FIG. 14C illustrates a top view of a photo-detecting device, accordingto some embodiments. FIG. 14D illustrates a cross-sectional view alongan A-A′ line in FIG. 14C, according to some embodiments. FIG. 14Eillustrates a cross-sectional view along a B-B′ line in FIG. 14C,according to some embodiments. The photo-detecting device 1400 c in FIG.14C is similar to the photo-detecting device 300 a in FIG. 3A. Thedifference is described below. The absorption region 10 is fullyembedded in the substrate 20. The photo-detecting device 1400 c includesa passivation layer 1400 on the absorption region 10 and the substrate20, where the passivation layer 1400 is similar to the passivation layer1400 described in FIG. 14A. In some embodiments, the thickness of thepassivation layer 1400 can be between 100 nm and 500 nm. The readoutelectrodes 330 a, 330 b and the control electrodes 340 a, 340 b are overthe first surface 1401 of the passivation layer 1400 and are separatedfrom the absorption region 10. In some embodiments, the readoutelectrodes 330 a, 330 b, the control electrodes 340 a, 340 b and thesecond electrode 60 are coplanarly formed on the passivation layer 1400,and thus a height difference between the electrodes can be reduced. Thecarrier conducting layer is in the passivation layer 1400 instead of thesubstrate 20. That is, the heterointerface is between the passivationlayer 1400 and the absorption region 10. In some embodiments, the firstsurface 11 of the absorption region 10 is at least partially in directcontact with the passivation layer 1400 and thus the heterointerface isformed between the absorption region 10 and the passivation layer 1400.The substrate 20 may be intrinsic and may not be limited to thedescription in FIG. 1A.

In some embodiments, the second doped region 108 is similar to thesecond doped region 108 describe in FIG. 3A. The difference is describedbelow. The second doped region 108 is in passivation layer 1400 and inthe absorption region 10. In some embodiments, the second doped region108 has a depth equal to or greater than a thickness of the passivationlayer 1400, so as to guide the carriers with the second type to movetowards the second electrode 60 and to be further evacuated by acircuit. The depth is measured from the first surface 1401 of thepassivation layer 1400, along a direction substantially perpendicular tothe first surface 1401 of the passivation layer 1400. The depth is to aposition where the dopant profile of the fourth dopant reaches a certainconcentration, such as 1×10¹⁵ cm⁻³.

Similar to the photo-detecting device 100 a in FIG. 1A, in someembodiments, a doping concentration of the first dopant at theheterointerface between the absorption region 10 and the carrierconducting layer, that is the passivation layer 1400 in some embodiment,is equal to or greater than 1×10¹⁶ cm⁻³. In some embodiments, the dopingconcentration of the first dopant at the heterointerface can be between1×10¹⁶ cm⁻³ and 1×10²⁰ cm⁻³ or between 1×10¹⁷ cm⁻³ and 1×10²⁰ cm⁻³. Insome embodiments, a doping concentration of the second dopant at theheterointerface is lower than the doping concentration of the firstdopant at the heterointerface. In some embodiments, a dopingconcentration of the second dopant at the heterointerface between 1×10¹²cm⁻³ and 1×10¹⁷ cm⁻³.

In some embodiment, the concentration of the graded doping profile ofthe first dopant is gradually deceased from the second surface 12 to thefirst surface 11 of the absorption region 10 so as to facilitate themoving of the carriers, such as the electrons if the first doped regions302 a, 302 b are of n-type.

In some embodiments, the first switch (not labeled) and the secondswitch (not labeled) are partially formed in the carrier conductinglayer, that is the passivation layer 1400 in some embodiments. In someembodiments, the first doped regions 302 a, 302 b are in the passivationlayer 1400. In some embodiments, the third peak doping concentrations ofthe first doped regions 302 a, 302 b lie in the passivation layer 1400.

In some embodiments, the depth of each of the first doped regions 302 a,302 b is less than a thickness of the passivation layer 1400. The depthis measured from the first surface 1401 of the passivation layer 1400 toa position where the dopant profile reaches a certain concentration,such as 1×10¹⁵ cm⁻³.

In some embodiments, the absorption function and the carrier controlfunction such as demodulation of the carriers and collection of thecarriers operate in the absorption region 10 and the carrier conductinglayer, that is, the passivation layer 1400 in some embodiments,respectively.

In some embodiments, a conducting region 201 can be formed in thecarrier conducting layer, that is the passivation layer 1400 in someembodiments. The conducting region 201 can be similar to the conductingregion 201 described in FIG. 3A, such as the conducting region 201 isoverlapped with a portion of the first doped regions 302 a, 302 b in thepassivation layer 1400. The difference is described below. In someembodiments, the conducting region 201 has a depth equal to or greaterthan a thickness of the passivation layer 1400, so as to confine andguide the carriers with the first type to move towards one of the firstdoped regions 302 a, 302 b. The depth is measured from the first surface1401 of the passivation layer 1400, along a direction substantiallyperpendicular to the first surface 1401 of the passivation layer 1400.The depth is to a position where the dopant profile of the second dopantreaches a certain concentration, such as 1×10¹⁵ cm⁻³.

In some embodiments, a width of the absorption region 10 is less than adistance between the distance between the two control electrodes 340 a,340 b, which can reduce the leakage current between the two controlelectrodes 340 a, 340 b. FIG. 14F illustrates a cross-sectional view ofa photo-detecting device, according to some embodiments. Thephoto-detecting device 1400 f in FIG. 14F is similar to thephoto-detecting device 1400 e in FIG. 14E. The difference is describedbelow. The absorption region 10 is partially embedded in the substrate20. The passivation layer 1400 is conformally formed on the absorptionregion 10 and the substrate 20 to cover the exposed side surfaces 13 ofthe absorption region 10. The conducting region 201 can surround theabsorption region 10 or overlapped with all of the surfaces of theabsorption region 10, that is, overlapped with the first surface 11, thesecond surface 12, and all of the side surfaces 13 of the absorptionregion 10.

In some embodiments, the depth of each of the first doped regions 302 a,302 b is greater than a thickness of the passivation layer 1400. Thedepth is measured from the first surface 1401 of the passivation layer1400 to a position where the dopant profile reaches a certainconcentration, such as 1×10¹⁵ cm⁻³. In some embodiments, the depth ofeach of the first doped regions 302 a, 302 b is less than a thickness ofthe passivation layer 1400. The depth is measured from the first surface1401 of the passivation layer 1400 to a position where the dopantprofile reaches a certain concentration, such as 1×10¹⁵ cm⁻³.

FIG. 14G illustrates a top view of a photo-detecting device, accordingto some embodiments. FIG. 14H illustrates a cross-sectional view alongan A-A′ line in FIG. 14G, according to some embodiments. FIG. 14Iillustrates a cross-sectional view along a B-B′ line in FIG. 14G,according to some embodiments. The photo-detecting device 1400 g in FIG.14G is similar to the photo-detecting device 1400 c in FIG. 14C. Thedifference is described below. The second doped region 108 is in thesubstrate 20. In other words, the fourth peak doping concentration ofthe second doped region 108 lies in the substrate 20. In someembodiment, the second doped region 108 is below the first surface 1401of the passivation layer 1400 and is in direct contact with theabsorption region 10, for example, the second doped region 108 may be incontact with or overlapped with one of the side surfaces 13 of theabsorption region 10. As a result, the carriers generated from theabsorption region 10 can move from the absorption region 10 towards thesecond doped region 108 through the heterointerface between theabsorption region 10 and the substrate 20. The second electrode 60 isover the first surface 1401 of the passivation layer 1400.

FIG. 14J illustrates a top view of a photo-detecting device, accordingto some embodiments. FIG. 14K illustrates a cross-sectional view alongan A-A′ line in FIG. 14J, according to some embodiments. FIG. 14Killustrates a cross-sectional view along a B-B′ line in FIG. 14J,according to some embodiments. The photo-detecting device 1400 j in FIG.14J is similar to the photo-detecting device 1400 g in FIG. 14G. Thedifference is described below. In some embodiments, a width of theconducting region 201 is less than a distance between the distancebetween the two control electrodes 340 a, 340 b. The second doped region108 may surround at least a portion of the absorption region 10. Thesecond doped region 108 may block photo-generated charges in theabsorption region 10 from reaching the substrate 20, which increases thecollection efficiency of photo-generated carriers of the photo-detectingdevice 1400 f. The second doped region 108 may also blockphoto-generated charges in the substrate 20 from reaching the absorptionregion 10, which increases the speed of photo-generated carriers of thephoto-detecting device 1400 j. The second doped region 108 may include amaterial the same as the material of the absorption region 10, the sameas the material of the substrate 20, a material as a combination of thematerial of the absorption region 10 and the material of the substrate20, or different from the material of the absorption region 10 and thematerial of the substrate 20. In some embodiments, the shape of thesecond doped region 108 may be but not limited to a ring. In someembodiments, the second doped region 108 may reduce the cross talkbetween two adjacent pixels of the photo-detecting apparatus.

In some embodiments, the second doped region 108 extends to reach thefirst surface 21 of the substrate 20.

FIG. 15A shows a gain component 1500 a with two-terminals. The gaincomponent 1500 a includes a lightly-doped-region 1510 (e.g., n-region,e.g., 1e14 to 1e17 cm′), an emitter region 1520 and a collector region1530.

The collector region 1530 is for collecting carriers, and is coupled toa collector electrode (C). The collector region 1530 is of aconductivity type such as heavily p-doped (p++, e.g., 1e18 to 1e21cm⁻³). The emitter region 1520 is for emitting carriers, and is coupledto an emitter electrode (E). The emitter region 1520 is of aconductivity type such as heavily p-doped (p++).

The material of lightly-doped-region 1510, emitter region 1520, thecollector region 1530 can be silicon, germanium, silicon-germanium, orIII-V materials.

A method for amplifying photo-carriers received by the gain component1500 a includes the steps of: applying a first voltage (e.g., a positivevoltage) to the emitter electrode E; applying a second voltage (e.g.,ground) to the collector electrode C; a forward-bias is thus createdacross the p-n junction between the emitter region 1520 and thelightly-doped region 1510, and a reverse-bias is thus created across thep-n junction between the collector region 1530 and the lightly-dopedregion 1510 to collect an electrical signal (e.g., hole current) fromthe emitter; receiving a first type of carriers (e.g., electrons fromoutside the gain component 1500 a) in the lightly-doped region 1510,which increase the forward-bias between the emitter region 1520 and thelightly-doped region 1510; collecting a second type of carriers (e.g.,holes) emitted from the emitter region 1520 by the collector region 1530as an amplified electrical signal (e.g., an amplified hole current).

As a result, the gain component provides an amplified electrical signalin the collector region based on the received carriers in thelightly-doped region, which improves signal to noise ratio.

FIG. 15B shows another implementation of the gain component 1500 b,where the emitter region 1520 is surrounded by a moderately-doped region1540 (e.g., n+ region, e.g., 1e16 to 1e19 cm³).

FIG. 15C shows another implementation of the gain component 1500 c,where the collector region 1530 is surrounded by a moderately-dopedregion 1540 (e.g., n+ region, e.g., 1e16 to 1e19 cm⁻³).

FIG. 15D shows another implementation of the gain component 1500 d,where the emitter region 1520 and the collector region 1540 aresurrounded by a moderately-doped region (e.g., n+ region, e.g., 1e16 to1e19 cm³).

FIG. 16A shows a gain component 1600 a with three terminals. The gaincomponent 1600 a includes a lightly-doped-region 1610 (e.g., n-region),an emitter region 1620, a base region 1640, and a collector region 1630.

The collector region 1630 is for collecting carriers, and is coupled toa collector electrode (C). The collector region 1630 is of aconductivity type such as heavily p-doped (p++). The base region 1640 iscoupled to a base electrode (B), and is of a conductivity type such asheavily n-doped (n++). The emitter region 1620 is for emitting carriers,and is coupled to an emitter electrode (E). The emitter region 1620 isof a conductivity type such as heavily p-doped (p++).

The material of lightly-doped-region 1610, emitter region 1620, baseregion 1640, and collector region 1630 can be silicon, germanium,silicon-germanium, or III-V materials.

A method for amplifying photo-carriers received by the gain componentincludes the steps of: establishing a first voltage difference betweenthe emitter electrode E and the base electrode B to form aforward-biased p-n junction; establishing a second voltage differencebetween the collector electrode C and the base electrode B to form areverse-biased p-n junction; receiving a first type of carriers (e.g.,electrons from outside of the gain component 1600 a) in thelightly-doped region 1610; increasing the first voltage difference toform another forward-biased p-n junction; collecting a second type ofcarriers (e.g., holes) emitting from the emitter region 1620 by thecollector region 1630 as an amplified electrical signal.

As a result, the gain component 1600 a provides an amplified electricalsignal in the collector region 1630 based on the received carriers inthe lightly-doped region 1610, which improves signal to noise ratio.

FIG. 16B shows another implementation of the gain component 1600 b,where the emitter region 1620 and the base region 1640 are surrounded bya moderately-doped region 1650 (e.g., n+ region).

FIG. 16C shows another implementation of the gain component 1600 c,where the collector region 1630 and the base region 1640 are surroundedby a moderately-doped region 1650 (e.g., n+ region).

FIG. 16D shows another implementation of the gain component 1600 d,where the emitter region 1620, the base region 1640, and the collectorregion 1630 are surrounded by a moderately-doped region 1610 (e.g., n+region).

FIG. 17A shows a complementary metal-oxide-semiconductor (CMOS) imagesensor 1700 a (or a photo-detecting apparatus) that includes alightly-doped region 1710 (e.g., n-Si), an absorption region 1720 (e.g.,p-Ge), and gain component 1730 (e.g., Si). The gain component 1730 canbe a two-terminal or a three-terminal gain component as described inFIGS. 15A-15D and 16A-16D.

The absorption region 1720 or the lightly-doped region 1710 can be aGroup III-V semiconductor material (e.g., InGaAs, GaAs/AlAs, InP/InGaAs,GaSb/InAs, or InSb), a semiconductor material including a Group IVelement (e.g., Ge, Si or Sn), a compound such as Si_(x)Ge_(y)Sn_(1-x-y),(0≤x≤, 0≤y≤1), or Ge_(1-a)Sn_(a) (0≤a≤0.1), or Ge_(1-x)Si_(x) (0≤x≤0.1).

In some embodiments, a bandgap of the lightly-doped region 1710 (e.g.,n-Si) is greater than a bandgap of the absorption region 1720 (e.g.,p-Ge). The gain component 1730 is for collecting photo-carriers togenerate an amplified electrical signal. The absorption region 1720includes a first dopant having a first peak doping concentration. Thelightly-doped region 1710 includes a second dopant having a second peakdoping concentration lower than the first peak doping concentration toreduce the dark current of the CMOS image sensor 1700 a (e.g., below 10pA).

The first peak doping concentration can be between 1×10¹⁷ cm⁻³ and1×10²⁰ cm⁻³. In some embodiments, a ratio of the first peak dopingconcentration to the second peak doping concentration is equal to ormore than 10 such that the CMOS image sensor 1701 exhibits low darkcurrent (e.g., less than or equal to 10 pA) and high quantum efficiency.The absorption region 1720 can have a gradient doping profile, where thefirst peak doping is far from the interface between the absorptionregion 1720 and the lightly-doped region 1710.

The absorption region 1720 can include a heavily doped region 1722(e.g., p++) coupled to a voltage (e.g., ground). The lightly-dopedregion 1710 can receive a first type of photo-carriers (e.g.,electrons), and the heavily doped region 1722 can receive a second typeof photo-carriers (e.g., holes).

A method for amplifying photo-carriers received by the gain component1730 includes the steps of: receiving a photo-signal in an absorptionregion 1720 (e.g., p-Ge) to generate photo-carriers having a first and asecond type (e.g., electrons and holes); steering the first type ofphoto-carriers (e.g., electrons) to a gain region 1730; and generatingan amplified electrical signal having the second type (e.g., holes).

As such, the CMOS image sensor 1701 provides an amplified electricalsignal based on the optical signal and improves signal to noise ratio.

In some implementations, the light absorption region can be covered (asshown in the dashed line) by a different material 1750 (e.g., poly-Si).

FIG. 17B shows an implementation of the CMOS sensor 1700 b, where thelight absorption region 1720 is partially embedded in the lightly-dopedregion 1710.

FIG. 17C shows an implementation of the CMOS sensor 1700 c, where thelight absorption region 1720 is fully embedded in the lightly-dopedregion 1710.

Similar to FIG. 17A, FIG. 18A shows a CMOS image sensor 1800 a thatincludes a lightly-doped region 1810 (e.g., n-Si), an absorption region1820 (e.g., p-Ge), and gain component 1830 (e.g., Si). The gaincomponent 1830 can be a two-terminal or a three-terminal gain componentas described in FIGS. 15A-15D and 16A-16D.

The lightly-doped region 1810 can include a heavily doped region 1822(e.g., p++) that is coupled to a voltage (e.g., ground). Thelightly-doped region 1810 can receive both a first type ofphoto-carriers (e.g., electrons) and a second type of photo-carriers(e.g., holes). The first type photo-carriers are directed to the gaincomponent 1830, while the second type of photo-carriers are collected bythe heavily doped region 1822.

A method for amplifying photo-carriers received by the gain component1830 includes the steps of: receiving a photo-signal in an absorptionregion 1820 (e.g., p-Ge) to generate photo-carriers having a first and asecond type (e.g., electrons and holes); steering the first type ofphoto-carriers (e.g., electrons) to a gain region 1830; and generatingan amplified electrical signal having the second type (e.g., holes).

As such, the CMOS image sensor 1800 a provides an amplified electricalsignal based on the optical signal and improves signal to noise ratio.

In some implementations, the light absorption region 1820 can be covered(as shown in the dashed line) by a different material (e.g., poly-Si).

FIG. 18B shows an implementation of the CMOS sensor 1800 b, where thelight absorption region is partially embedded in the lightly-dopedregion 1810.

FIG. 18C shows an implementation of the CMOS sensor 1800 c, where thelight absorption region is fully embedded in the lightly-doped region1810.

FIG. 19A shows a photo-detecting apparatus 1900 a with gain. Thephoto-detecting apparatus 1900 a includes a lightly-doped region 1910(e.g., n-Si), an absorption region 1920 (e.g., p-Ge), two gaincomponents 1930 a and 1930 b, and two control regions 1940 a and 1940 b(shown as p++, but can be can be undoped or lightly doped) each coupledwith a control terminal (M1 and M2). The gain components 1930 a, 1930 bcan be a two-terminal or a three-terminal gain component as described inFIGS. 15A-15D and 16A-16D.

The absorption region 1920 or the lightly-doped region 1910 can be aGroup III-V semiconductor material (e.g., InGaAs, GaAs/AlAs, InP/InGaAs,GaSb/InAs, or InSb), a semiconductor material including a Group IVelement (e.g., Ge, Si or Sn), a compound such as Si_(x)Ge_(y)Sn_(1-x-y),(0≤x≤1, 0≤y≤1), or Ge_(1-a)Sn_(a) (0≤a≤0.1).

In some embodiments, a bandgap of the lightly-doped region 1910 (e.g.,n-Si) is greater than a bandgap of the absorption region 1920 (e.g.,p-Ge). The gain components 1930 a, 1930 b are for collectingphoto-carriers to generate an amplified electrical signal. Theabsorption region 1920 includes a first dopant having a first peakdoping concentration. The lightly-doped region 1910 includes a seconddopant having a second peak doping concentration lower than the firstpeak doping concentration to reduce the dark current of thephoto-detecting apparatus 1900 a (e.g., below 10 pA).

The first peak doping concentration and the second peak concentrationcan be similar to the examples described in FIG. 17A.

The absorption region 1920 can include a heavily doped region 1922(e.g., p++) coupled to a voltage V0 (e.g., ground). The lightly-dopedregion 1910 can receive a first type of photo-carriers (e.g.,electrons), and the heavily doped region 1922 can receive a second typeof photo-carriers (e.g., holes).

The control signals M1 and M2 can steer the first type of photo-carrierstowards one of the gain components 1930 a or 1930 b.

A method for amplifying photo-carriers received by the gain componentincludes the steps of: receiving a photo-signal in an absorption region1920 (e.g., p-Ge) to generate photo-carriers having a first and a secondtype (e.g., electrons and holes); steering the first type ofphoto-carriers (e.g., electrons) to a gain region 1930 a or 1930 b; andgenerating an amplified electrical signal having the second type (e.g.,holes).

As such, the photo-detecting apparatus 1900 a provides an amplifiedelectrical signal based on the optical signal and improves signal tonoise ratio.

In some implementations, the light absorption region 1920 can be covered(not shown here) by a different material (e.g., poly-Si).

In some implementations, the light absorption region 1920 can bepartially (e.g., similar to the absorption region 1720 as shown in FIG.17B) or fully embedded (e.g., similar to the absorption region 1730 asshown in FIG. 17C) in the lightly-doped region 1910.

FIG. 19B shows a photo-detecting apparatus 1900 b with gain. Thephoto-detecting apparatus 1900 b is similar to the photo-detectingapparatus 1900 a in FIG. 19A, except that the control regions arecombined with the emitter regions, such that the emitter signal (E) canbe used to steer the carriers and to amplify the carriers.

FIG. 20A shows an example top view of the photo-detecting apparatus 2000a with gain, such as described in FIG. 19A or FIG. 19B, where thelightly-doped region is the substrate 2010.

FIG. 20B shows an example top view of the photo-detecting apparatus 2000b with gain, such as described in FIG. 19A or FIG. 19B, where thesubstrate 2010 can be intrinsic (e.g., i-Si), lightly p-doped (p-Si), orlightly n-doped (n-Si). The lightly-doped region 2012 (e.g., n-Si) canbe formed in the substrate 2010 by implant or diffusion or othersuitable fabrication method. In some implementations, a portion of theabsorption region 2020 (e.g., p-Ge) can be formed on a region of thesubstrate 2010 that is not the lightly-doped region 2012. The absorptionregion 2020 can be coupled to the lightly-doped region 2012 through alightly-doped path 2030 (e.g., n-Si) formed between the absorptionregion 2020 and the substrate 2010. The photo-carriers (e.g., electrons)generated by the absorption region 2020 can drift from the absorptionregion 2020 to the lightly-doped region 2012, where one of the gaincomponents can then generate an amplified electrical signal based on thecontrol signals. Accordingly, the photo-detecting apparatus 2000 b canbe formed in a substrate with intrinsic, lightly p-doping, and lightlyn-doping.

FIG. 21 shows a photo-detecting apparatus 2100 a with gain. Thephoto-detecting apparatus 2100 a includes a lightly-doped region 2110(e.g., n-Si) formed in a substrate 2150 (e.g., n-Si, p-Si, or intrinsicSi), an absorption region 2120 (e.g., p-Ge), two gain components 2130 aand 2130 b, and two control regions 2140 a and 2140 b (shown as p++, butcan be undoped or lightly doped) each coupled with a control terminal(M1 and M2). The gain component 2130 a, 2030 b can be a two-terminal ora three-terminal gain component as described in FIGS. 15A-15D and16A-16D.

Accordingly, the photo-detecting apparatus 2100 a can be formed in asubstrate 2150 with intrinsic, lightly p-doping, and lightly n-doping.

The absorption region 2120 or the lightly-doped region 2110 can beformed using materials as described in FIG. 19A.

In some embodiments, the lightly-doped region 2110 may partially orcompletely overlap the two control regions 2140 a and 2140 b.

The absorption region can include a heavily doped region 2122 (e.g.,p++) coupled to a voltage V0 (e.g., ground). The lightly-doped region2110 can receive a first type of photo-carriers (e.g., electrons), andthe heavily doped region 2122 can receive a second type ofphoto-carriers (e.g., holes).

The control signals M1 and M2 steers the first type of photo-carrierstowards one of the gain components 2130 a or 2130 b, as described inreference to FIG. 19A.

In some implementations, the light absorption region 2120 can be covered(not shown here) by a different material (e.g., poly-Si).

In some implementations, the light absorption region 2120 can bepartially (e.g., similar to the absorption region 1720 as shown in FIG.17B) or fully embedded (e.g., similar to the absorption region 1720 asshown in FIG. 17C) in the lightly-doped region 2110.

In some implementations, similar to FIG. 19B, the control regions 2140 aand 2140 b can be combined with the emitter regions, such that theemitter signal (E) can be used to steer the carriers and to amplify thecarriers.

FIG. 22A shows an example top view of the photo-detecting apparatus 2200a with gain, such as the photo-detecting apparatus 2100 a described inFIG. 21. and FIG. 22B shows an example top view of the photo-detectingapparatus 2200 b with gain, such as the photo-detecting apparatus 2100 adescribed in FIG. 21, where a portion of the absorption region 2120(e.g., p-Ge) can be formed on a region of the substrate 2150 that is notthe lightly-doped region 2110. The lightly doped region 2110 (e.g.,n-Si) can be formed in the substrate 2150 by implant or diffusion orother suitable fabrication method. The absorption region 2120 can becoupled to the lightly-doped region 2110 through a lightly-doped path2230 (e.g., n-Si) formed between the absorption region 2120 and thesubstrate 2150. The photo-carriers (e.g., electrons) generated by theabsorption region 2120 can drift from the absorption region 2120 to thelightly-doped region 2110, where one of the gain components can thengenerate an amplified electrical signal (e.g., hole current) based onthe control signals.

FIG. 23A shows an example top view of the photo-detecting apparatus 2300a with gain, where similar to FIGS. 18A-18C, the heavily doped region2322 (e.g., p++) is formed in the lightly doped region 2310 (e.g., n-Si)instead of in absorption region 2320 (e.g., p-Ge). The lightly-dopedregion 2310 can receive both a first type of photo-carriers (e.g.,electrons) and a second type of photo-carriers (e.g., holes). The firsttype photo-carriers are directed to the gain components 2330 a or 2330 bbased on the control signals 2340 a or 2340 b, while the second type ofphoto-carriers are collected by the heavily doped region 2322.

FIG. 23B shows another example top view of the photo-detecting apparatus2300 b with gain that is similar to FIG. 23A, but where a portion of theabsorption region 2320 (e.g., p-Ge) can be formed on a region of thesubstrate 2312 that is not the lightly-doped region 2310. The absorptionregion 2320 can be coupled to the lightly-doped region 2310 through alightly-doped path 2350 (e.g., n-Si) formed between the absorptionregion 2320 and the substrate 2312. The photo-carriers (e.g., electrons)generated by the absorption region 2320 can drift from the absorptionregion 2320 to the lightly-doped region 2310, where one of the gaincomponents 2330 a or 2330 b can then generate an amplified electricalsignal (e.g., hole current) based on the control signals 2340 a or 2340b.

FIG. 24A shows an example top view of the photo-detecting apparatus 2400a with gain, which is similar to FIG. 22A, but the heavily doped region2422 (e.g., p++) is formed outside (e.g., similar to those shown inFIGS. 18A-18C) of the light absorption region 2420 (e.g., p-Ge). Aportion of the absorption region 2420 (e.g., p-Ge) can be formed on aregion of the substrate 2450 that is not the lightly-doped region 2410.The lightly doped region 2410 can partially overlap with the two controlregions 2440 a and 2440 b (e.g., p++) adjacent to the gain components2430 a and 2430 b. The photo-carriers (e.g., electrons) generated by theabsorption region 2420 can drift from the absorption region 2420 to thelightly-doped region 2410, where one of the gain components 2430 a or2430 b can then generate an amplified electrical signal (e.g., holecurrent) based on the control signals.

FIG. 24B shows another example top view of the photo-detecting apparatus2400 b with gain that is similar to FIG. 22B, where the heavily dopedregion 2422 (e.g., p++) is formed outside (e.g., similar to those shownin FIGS. 18A-18C) of the light absorption region 2420 (e.g., p-Ge). Theabsorption region 2420 can be coupled to the lightly-doped region 2410through a lightly-doped path 2460 (e.g., n-Si) formed between theabsorption region 2420 and the substrate 2450. The photo-carriers (e.g.,electrons) generated by the absorption region 2420 can drift from theabsorption region 2420 to the lightly-doped region 2410, where one ofthe gain components 2430 a or 2430 b can then generate an amplifiedelectrical signal (e.g., hole current) based on the control signals 2440a and 2440 b.

FIGS. 25A-25C illustrate cross-sectional views of a portion of aphoto-detecting device, according to some embodiments. Thephoto-detecting device can include a structure substantially the same asany embodiments described before. In some embodiments, if notspecifically mentioned in the previous description, referring to FIG.25A, the absorption region 10 can be entirely on the first surface 21 ofthe substrate 20. Referring to FIG. 25B, the absorption region 10 can bepartially embedded in the substrate 20. That is, a part of each of theside surfaces are in contact with the substrate 20. Referring to FIG.25C, the absorption region 10 can be entirely embedded in the substrate20. That is, the side surfaces are in contact with the substrate 20.

FIGS. 26A-26D show the examples of the control regions C1, C2, C3, C4 ofa photo-detecting device according to some embodiments. Thephoto-detecting device can include a structure substantially the same asany embodiments described before.

Referring to FIG. 26A, in some embodiments, the control electrode 340can be over the first surface 21 of the substrate 20 with an intrinsicregion right under the control electrode 340. The control electrode 340may lead to formation of a Schottky contact, an Ohmic contact, or acombination thereof having an intermediate characteristic between thetwo, depending on various factors including the material of thesubstrate 20 or the material of the passivation layer and/or thematerial of the control electrode 340 and/or the dopant or defect levelof the substrate 20 or the passivation layer 1400. The control electrode340 may be any one of the control electrodes 340 a, 340 b, 340 c, 340 d.

Referring to FIG. 26B, in some embodiments, the control region of theswitch further includes a doped region 303 under the control electrodes340 and in the substrate 20. In some embodiments, the doped region 303is of a conductivity type different from the conductivity type of thefirst doped regions 302 a, 302 b. In some embodiments, the doped region303 include a dopant and a dopant profile. The peak dopantconcentrations of the doped region 303 depend on the material of thecontrol electrode 340 and/or the material of the substrate 20 and/or thedopant or defect level of the substrate 20, for example, between 1×10¹⁷cm⁻³ to 5×10²⁰ cm⁻³. The doped region 303 forms a Schottky or an Ohmiccontact or a combination thereof with the control electrode 340. Thedoped region is for demodulating the carriers generated from theabsorption region 10 based on the control of the control signals. Thecontrol electrode 340 may be any one of the control electrodes 340 a,340 b, 340 c, 340 d.

Referring to FIG. 26C, in some embodiments, the control region of theswitch further includes a dielectric layer 350 between the substrate 20and the control electrode 340. The dielectric layer 350 prevents directcurrent conduction from the control electrode 340 to the substrate 20,but allows an electric field to be established within the substrate 20in response to an application of a voltage to the control electrode 340.The established electric field between two of the control regions, forexample, between the control regions C1, C2, may attract or repel chargecarriers within the substrate 20. The control electrode 340 may be anyone of the control electrodes 340 a, 340 b, 340 c, 340 d.

Referring to FIG. 26D, in some embodiments, the control region of theswitch further includes a doped region 303 under the control electrodes340 and in the substrate 20, and also includes a dielectric layer 350between the substrate 20 and the control electrode 340. The controlelectrode 340 may be any one of the control electrodes 340 a, 340 b, 340c, 340 d.

In some embodiments, the region of the carrier conducting layer rightunder the readout electrode may be intrinsic. For example, the region ofthe substrate right under the readout electrode of each of the switchesmay be intrinsic. For another example, the region of the passivationlayer right under the readout electrode of each of the switches may beintrinsic. The readout electrode may lead to formation of a Schottkycontact, an Ohmic contact, or a combination thereof having anintermediate characteristic between the two, depending on variousfactors including the material of the substrate 20 or the material ofthe passivation layer 1400 or the material of the passivation layerand/or the material of the readout electrode and/or the dopant or defectlevel of the substrate 20 or the passivation layer 1400.

In some embodiments, the dielectric layer 350 may include, but is notlimited to SiO₂. In some embodiments, the dielectric layer 350 mayinclude a high-k material including, but is not limited to, Si₃N₄, SiON,SiN_(x), SiO_(x), GeO_(x), Al₂O₃, Y₂O₃, TiO₂, HfO₂ or ZrO₂. In someembodiments, the dielectric layer 350 may include semiconductor materialbut is not limited to amorphous Si, polycrystalline Si, crystalline Si,germanium-silicon, or a combination thereof.

In some embodiments, the conducting region 201 of the photo-detectingdevice can be any suitable design. Taking the conducting region 201 ofthe photo-detecting device in FIGS. 3A-3B, 4A-4C, 5A-5C, 6A-6G, 7A-7E,8A-8E, 14C-14L as an example, a width of the conducting region 201 canbe less than a distance between the control electrodes 340 a, 340 b. Insome embodiments, the conducting region 201 may not be overlapped withany portion of the two doped regions 303 described in FIGS. 26B and 26D.In some embodiments, the conducting region 201 may be overlapped with aportion of the two doped regions 303 described in FIGS. 26B and 26D. Insome embodiments, the conducting region 201 may be overlapped with theentire doped regions 303 described in FIGS. 26B and 26D. In someembodiments, the conducting region 201 may not be overlapped with anyportion of each of the first doped regions 302 a, 302 b. In someembodiments, the conducting region 201 may be overlapped with a portionof each of the first doped regions 302 a, 302 b. In some embodiments,the conducting region 201 may be overlapped with the entire first dopedregions 302 a, 302 b.

Taking the conducting region 201 of the photo-detecting device in FIGS.10A, and 11A as another example, the conducting region 201 may not beoverlapped with any portion of the third contact region 208. In someembodiments, the conducting region 201 may be overlapped with a portionof the third contact region 208. In some embodiments, the conductingregion 201 may be overlapped with the entire third contact region 208.In some embodiments, the conducting region 201 may not be overlappedwith any portion of the first contact region 204. In some embodiments,the conducting region 201 may be overlapped with a portion of the firstcontact region 204. In some embodiments, the conducting region 201 maybe overlapped with the entire first contact region 204.

Taking the conducting region 201 of the photo-detecting device in FIGS.1A-1D, and 2A-2F as another example, the conducting region 201 may notbe overlapped with any portion of the first doped region 102. In someembodiments, the conducting region 201 may be overlapped with a portionof the first doped region 102. In some embodiments, the conductingregion 201 may be overlapped with the entire the first doped region 102.

In some embodiments, any photo-detecting device mentioned above, forexample, the photo-detecting device in FIGS. 1A-11E, 13A-26D, mayinclude a waveguide similar to the waveguide 206 described in FIGS.12A-12C, for guiding and/or confining the incident optical signalpassing through a defined region of the substrate 20. FIG. 27A is ablock diagram of an example embodiment of an imaging system. The imagingsystem may include an imaging module and a software module configured toreconstruct a three-dimensional model of a detected object. The imagingsystem or the imaging module may be implemented on a mobile device(e.g., a smartphone, a tablet, vehicle, drone, etc.), an ancillarydevice (e.g., a wearable device) for a mobile device, a computing systemon a vehicle or in a fixed facility (e.g., a factory), a roboticssystem, a surveillance system, or any other suitable device and/orsystem.

The imaging module includes a transmitter unit, a receiver unit, and acontroller. During operation, the transmitter unit may emit an emittedlight toward a target object. The receiver unit may receive reflectedlight reflected from the target object. The controller may drive atleast the transmitter unit and the receiver unit. In someimplementations, the receiver unit and the controller are implemented onone semiconductor chip, such as a system-on-a-chip (SoC). In some cases,the transmitter unit is implemented by two different semiconductorchips, such a laser emitter chip on III-V substrate and a Si laserdriver chip on Si substrate.

The transmitter unit may include one or more light sources, controlcircuitry controlling the one or more light sources, and/or opticalstructures for manipulating the light emitted from the one or more lightsources. In some embodiments, the light source may include one or moreLEDs or vertical cavity surface emitting lasers (VCSELs) emitting lightthat can be absorbed by the absorption region in the photo-detectingapparatus. For example, the one or more LEDs or VCSEL may emit lightwith a peak wavelength within a visible wavelength range (e.g., awavelength that is visible to the human eye), such as 570 nm, 670 nm, orany other applicable wavelengths. For another example, the one or moreLEDs or VCSEL may emit light with a peak wavelength above the visiblewavelength range, such as 850 nm, 940 nm, 1050 nm, 1064 nm, 1310 nm,1350 nm, 1550 nm, or any other applicable wavelengths.

In some embodiments, the emitted light from the light sources may becollimated by the one or more optical structure. For example, theoptical structure may include one or more collimating lens.

The receiver unit may include one or more photo-detecting apparatusaccording to any embodiments as mentioned above. The receiver unit mayfurther include a control circuitry for controlling the controlcircuitry and/or optical structures for manipulating the light reflectedfrom the target object toward the one or more photo-detecting apparatus.In some implementations, the optical structure includes one or more lensthat receives a collimated light and focuses the collimated lighttowards the one or more photo-detecting apparatus.

In some embodiments, the controller includes a timing generator and aprocessing unit. The timing generator receives a reference clock signaland provides timing signals to the transmitter unit for modulating theemitted light. The timing signals are also provided to the receiver unitfor controlling the collection of the photo-carriers. The processingunit processes the photo-carriers generated and collected by thereceiver unit and determines raw data of the target object. Theprocessing unit may include control circuitry, one or more signalprocessors for processing the information output from thephoto-detecting apparatus, and/or computer storage medium that may storeinstructions for determining the raw data of the target object or storethe raw data of the target object. As an example, the controller in ani-ToF sensor determines a distance between two points by using the phasedifference between light emitted by the transmitter unit and lightreceived by the receiver unit.

The software module may be implemented to perform in applications suchas facial recognition, eye-tracking, gesture recognition, 3-dimensionalmodel scanning/video recording, motion tracking, autonomous vehicles,and/or augmented/virtual reality.

FIG. 27B shows a block diagram of an example receiver unit orcontroller. Here, an image sensor array (e.g., 240×180) may beimplemented using any implementations of the photo-detecting devicedescribed in reference to FIGS. 3A through 8E, FIGS. 14C through 14L. Aphase-locked loop (PLL) circuit (e.g., an integer-N PLL) may generate aclock signal (e.g., four-phase system clocks) for modulation anddemodulation. Before sending to the pixel array and externalillumination driver, these clock signals may be gated and/or conditionedby a timing generator for a preset integration time and differentoperation modes. A programmable delay line may be added in theillumination driver path to delay the clock signals.

A voltage regulator may be used to control an operating voltage of theimage sensor. For example, multiple voltage domains may be used for animage sensor. A temperature sensor may be implemented for the possibleuse of depth calibration and power control.

The readout circuit of the photo-detecting apparatus bridges each of thephoto-detecting devices of the image sensor array to a columnanalog-to-digital converter (ADC), where the ADC outputs may be furtherprocessed and integrated in the digital domain by a signal processorbefore reaching the output interface. A memory may be used to store theoutputs by the signal processor. In some implementations, the outputinterface may be implemented using a 2-lane, 1.2 Gb/s D-PHY MIPItransmitter, or using CMOS outputs for low-speed/low-cost systems.

An inter-integrated circuit (I2C) interface may be used to access all ofthe functional blocks described here.

FIGS. 28-31 disclose a flexible circuitry integration architecture foran optical sensor. An optical sensor (e.g., any of photo-detectingdevices, photo-detecting apparatuses, receiver unit, or imaging systemas disclosed in the present disclosure) typically operates along thefollowing steps. A photo-detecting element having one or more lightabsorption regions (e.g., silicon, germanium, III-V materials, etc.)receives an optical signal, and generates a photo-current in response tothe optical signal. An analog-front-end circuitry (e.g., a low-noisepreamplifier) then converts the photo-current at the current domain toan analog signal at the voltage domain. A transimpedance amplifier (TIA)circuitry then amplifies the analog signal at the voltage domain. Ananalog-to-digital converter (ADC) circuitry then converts the amplifiedanalog signal into a digital signal. The digital signal may be furtherprocessed by one or more processors (e.g., a microcontroller) and/orstored in a memory for the optical sensor's intended application(s).

When a photo-detecting element and the circuitry (e.g., CMOS circuitry)are designed by different entities (e.g., different companies), anintegration between the photo-detecting element and circuitry may bechallenging from a technical perspective. Using the analog-front-endcircuitry (AFE circuitry) as an example, operations of the AFE circuitryare highly dependent on various properties of the photo-detectingelement (e.g., dark current, operating bias, photo-responsivity,non-linearity, etc.). Therefore, the first entity that designs thephoto-detecting element would generally be the most suitable entity todesign the AFE circuitry. Moreover, the AFE circuitry convertselectrical signals from the current domain to the voltage domain, whichgenerally reduces the complexity of the designs of subsequent circuitry(e.g., digital circuitry) by the second entity. However, in many cases,the photo-detecting element is fabricated on a non-silicon material(e.g., III-V material) and therefore circuitry, which is typicallyfabricated on silicon, cannot be formed on the same material. To achievebetter integration, the design of the AFE circuitry often becomes theresponsibility of the second entity designing the rest of the circuitry.In such case, the circuit designer from the second entity, who may knowlittle about the photo-detecting element designed by the first entity,would need to gather many parameters related to the properties of thephoto-detecting element. The performance of the AFE circuitry may not beoptimized, and the overall design time may be increased. Accordingly,there exists a need for a technical solution to integrate circuitry ondifferent platforms for optical sensors. This disclosure describes agermanium-based optical sensor implemented on a germanium-on-siliconplatform that can be further integrated with circuitry implemented onmultiple silicon platforms. Such implementations provide severaltechnical advantages including smaller form factor (e.g., verticalstacking), lower system costs, reliable wafer-level integration, andsimplified circuit design (e.g., AFE circuitry designed and integratedwith photodetectors, providing an output to subsequent circuitry atvoltage domain, etc.).

FIG. 28 illustrates an example of an optical sensing apparatus 2800. Theoptical sensing apparatus 2800 includes a photodetector 2810 (e.g., anyof the photo-detecting device or apparatus described in this disclosure,such as photo-detecting device 100 a, 200 a, etc.). The photodetector2810 includes a first substrate 2812 formed using a first material(e.g., silicon), and an absorption region 2814 formed on or at leastpartially in the first substrate 2812. The absorption region 2814 isformed using a second material (e.g., germanium), where the absorptionregion 2814 is configured to receive an optical signal 2850 and togenerate a photo-current in response to receiving the optical signal2850. Using a germanium-on-silicon platform as an example,germanium-based materials (e.g., undoped/doped germanium,silicon-germanium compounds, etc.) may be deposited on a silicon-basedsubstrate or in pattern-etched trenches in the silicon-based substrateusing a CMOS-compatible fabrication process. The germanium-basedmaterials may be used as one or more absorption regions for detection ofnear-infrared (NIR) or short-wave infrared (SWIR) light (e.g., theoptical signal 2850).

As an example, photodetector 2810 may include a first substratecomprising silicon; a carrier conducting layer formed in the firstsubstrate; an absorption region composed of germanium and in contactwith the carrier conducting layer, the absorption region configured toreceive an optical signal and to generate photo-current in response tothe optical signal, where the absorption region is doped with a firstdopant having a first conductivity type and a first peak dopingconcentration, where the carrier conducting layer is doped with a seconddopant having a second conductivity type and a second peak dopingconcentration, where the carrier conducting layer is in contact with theabsorption region to form at least one heterointerface, and where aratio between the first peak doping concentration of the absorptionregion and the second peak doping concentration of the carrierconducting layer is equal to or greater than 10; and an electrode formedover the carrier conducting layer, where the electrode is separated fromthe absorption region, and wherein the electrode is configured tocollect a portion of the photo-current.

In some implementations, the absorption region 2814 may include an arrayof pixels. For example, a one-dimensional or a two-dimensional (e.g.,100 by 100 pixels, or any suitable numbers) germanium pixels (e.g., apixel of dimensions 3 μm by 3 μm, or any suitable area) may be formedon/in a silicon substrate to form one large photodetector (e.g., aphotodetector of dimensions 300 μm by 300 μm, or any suitable area). Insome implementations, the array of pixels can be electrically coupledtogether to generate one photo-current. In some other implementations,each pixel of the array of pixels can be electrically coupled to its owncircuitry for reading out the photo-current.

In some implementations, the photodetector 2810 further includes a lensarray (e.g., polymer or silicon lens as described in reference to FIGS.32A-32C) and/or one or more layers of anti-reflection coatingsconfigured to focus the optical signal 2850 to the array of pixels.

The photodetector 2810 further includes a second substrate 2816 bondedto the first substrate 2812, where the second substrate 2816 is formedusing the first material (e.g., silicon). Using a germanium-on-siliconplatform as an example, the first silicon substrate 2812 may be bondedto the second silicon substrate 2816 by wafer bonding.

The photodetector 2810 includes circuitry 2818 formed in the secondsubstrate 2816, where the circuitry 2818 is configured to convert thephoto-current and to an analog voltage output for processing. Forexample, the circuitry 2818 may include an AFE circuitry fabricatedusing a CMOS process. Referring to FIG. 29 as an example, the circuitry2900 includes a photodiode 2902, which can be a circuit-equivalent of agermanium-on-silicon platform (e.g., absorption region 2814 formed inthe substrate 2812) that provides a photocurrent in response toreceiving an optical signal. The circuitry 2900 further includes alow-noise preamplifier 2904, which converts the photocurrent to ananalog voltage output 2912 a.

The optical sensing apparatus 2800 further includes a third substrate2820 coupled to the photodetector 2810, where the third substrate 2820includes circuitry 2822 configured to process the analog voltage outputto generate a digital output. For example, the circuitry 2822 mayinclude an amplifier circuitry configured to amplify the voltage output,an analog-to-digital converter configured to convert the amplifiedvoltage output to a digital signal, and a micro-controller configured toprocess the digital signal.

In some implementations, the first substrate 2816 and the secondsubstrate 2820 may be bonded together by techniques such as flip-chipbonding. The circuitry 2818 and the circuitry 2822 may be electricallycoupled using electrical vias and bond pads between the second substrate2816 and the third substrate 2820. In some other implementations, thesecond substrate 2816 and the third substrate 2820 may be bondedtogether by wire-bonds.

In some implementations, any suitable portion of the circuitry 2822 maybe instead implemented in the circuitry 2818. For example, if there issufficient space on the second substrate 2816, the amplifier circuitry,the ADC circuitry, and/or the microcontroller unit (MCU) circuitry canbe implemented in the circuitry 2818. The circuitry 2822 can then beused to implement circuitry that is independent of the properties of theabsorption region 2814. Accordingly, the design of the circuitry can beflexible.

In some implementations, the optical sensing apparatus 2800 furtherincludes a light emitter 2830. The light emitter 2830 may beelectrically coupled to the circuitry 2818 or the circuitry 2822.

In some implementations, the circuitry 2818 further includes drivercircuitry for the light emitter 2830. Referring to FIG. 30 as anexample, the circuitry 3000 includes a photodiode 3002 (e.g., photodiode2902 in FIG. 29), which can be a circuit-equivalent of agermanium-on-silicon platform (e.g., absorption region 2814 formed inthe substrate 2812) that provides a photocurrent in response toreceiving an optical signal. The circuitry 3000 further includes alow-noise preamplifier 3004 (e.g., low-noise preamplifier 2904 in FIG.29), which converts the photocurrent to an analog voltage output 3012 a.The circuitry 3000 further includes driver circuitry 3006 configured todrive the light emitter 2830. Accordingly, a laser driver may beimplemented on the germanium-on-silicon platform to control a lightemitter 2830, where the circuitry 2822 may then be designed forapplication-specific circuitry instead of device-specific circuitry.This flexibility may enable the circuitry 2822 to be integrated withmultiple types of light emitter and photodetectors with minor circuitmodification.

FIG. 31 shows a block diagram of an example optical apparatus 3100 thatillustrates another non-limiting implementation of the circuitry 2818and the circuitry 2822. The circuitry 2818 and the absorption region2814 are formed on two bonded substrates, as described in reference toFIG. 28. In general, the circuitry 2818 can include optional customizedcircuitry blocks to fit different system and application requirements.In some implementations, the circuitry 2818 can include a programmableamplifier 3102 (e.g., the low-noise preamplifier 2904 plus anotherprogrammable amplifier, etc.) that receives a current input 3110 fromthe absorption region 2814 and outputs a corresponding analog voltageoutput 3120.

In some implementations, the circuitry 2818 can further include acurrent digital-to-analog converter (DAC) 3104 that receives a digitalsignal and converts the digital signal into an analog signal to drivethe light emitter 2830, which can be separate from or integrated on acommon substrate as the absorption region 2814 or the circuit 2818. Forexample, both the absorption region 2814 and the light emitter 2830 maybe fabricated based on germanium-on-silicon material on the firstsubstrate 2812. In some implementations, the circuitry 2818 and theabsorption region 2814 are integrated in one chip, where the absorptionregion 2814 is composed of germanium for light absorption. In someimplementations, the absorption region 2814 includes one or morephotodetectors composed of germanium for short wave infrared (SWIR)light absorption. In some implementations, the circuitry 2818 canfurther include a small power management unit (PMU) 3106 and a digitalinterface 3108 that receive signals from the second circuitry 2822 fordigital control.

In general, the circuitry 2822 can include any relevant circuitry (e.g.,analog-to-digital converter (ADC) 3116, fault detection circuitry 3114,temperature sensor 3112, PMU 3118, I2C/Digital Control/MODEM/EPROMcircuitry 3120, and/or any other relevant circuitry) that converts theanalog voltage output 3120 to a digital signal and processes theconverted digital signal for the intended application(s). In someimplementations, the ADC 3116 may include a multiplexer (MUX) that canreceive analog inputs from multiple sensors to implement multiplesensing functions.

FIG. 32A-32C discloses examples of high-index micro-lens array assemblyfor photodetectors (e.g., any of photo-detecting devices,photo-detecting apparatuses, receiver unit, or imaging system asdisclosed in the present disclosure). During packaging or assembling anoptical sensor component (e.g., chip or module) on a system (e.g.,printed circuit board), an encapsulation layer such as epoxy may be usedto cover the optical component in order to protect the opticalcomponent. The optical sensor component may include a micro-lens or amicro-lens array for guiding (e.g., focusing) light onto the sensor(s).The micro-lens may be formed using a polymer-based material, which mayhave an effective refractive index that is close to the effectiverefractive index of the encapsulation layer. As the result of the lowerrefractive index contrast, the designed performance (e.g., focal length)of the micro-lens may suffer. Accordingly, an optical sensing apparatus3200 (e.g., 3200 a, 3200 b, 3200 c) that addresses such technical issueis disclosed. The optical sensing apparatus 3200 includes a substrate3230 (e.g., Si, or the first substrate 2812 in FIG. 28); one or morepixels 3240 supported by the substrate, where each of the pixel 3240comprises an absorption region (e.g., Ge, or the absorption region 2814in FIG. 28) supported by the substrate, the absorption region configuredto receive an optical signal L and generate photo-carriers in responseto receiving the optical signal.

As an example, the optical sensing apparatus 3200 may include a firstsubstrate (e.g., substrate 3230) comprising silicon; a carrierconducting layer formed in the first substrate; an absorption regioncomposed of germanium and in contact with the carrier conducting layer,the absorption region configured to receive an optical signal and togenerate photo-current in response to the optical signal, where theabsorption region is doped with a first dopant having a firstconductivity type and a first peak doping concentration, where thecarrier conducting layer is doped with a second dopant having a secondconductivity type and a second peak doping concentration, where thecarrier conducting layer is in contact with the absorption region toform at least one heterointerface, and where a ratio between the firstpeak doping concentration of the absorption region and the second peakdoping concentration of the carrier conducting layer is equal to orgreater than 10; and an electrode formed over the carrier conductinglayer, where the electrode is separated from the absorption region, andwherein the electrode is configured to collect a portion of thephoto-current.

The optical sensing apparatus 3200 further comprises one or more lenses3260 over the respective pixel of the one or more pixels 3240, where theone or more lenses 3260 are composed of a first material (e.g., Si)having a first refractive index (e.g., >3 at the wavelength rangeabsorbed by the absorption region of the one or more pixels 3240). Theoptical sensing apparatus 3200 further comprises an encapsulation layer3292 over the one or more lenses and composed of a second material(e.g., polymer) having a second refractive index between 1.3 to 1.8,where a difference between the first refractive index and the secondrefractive index is above an index threshold such that a differencebetween an effective focal length of the one or more lenses 3260 and adistance between the one or more lenses 3260 and the one or more pixels3240 is within a distance threshold (e.g., 1%, 5%, or any otherthreshold that is tolerable by the system). As a result, the opticalsignal L can be converged and focused to enter the absorption region ofthe one or more pixels 3240.

In some embodiments, the first refractive index of the one or morelenses 3260 is not less than 3, where the difference between the firstrefractive index and the second refractive index of the encapsulationlayer 3292 is not less than 0.5, such that optical signal L can beconverged and focused to enter the absorption region of the one or morepixels 3240.

In some embodiments, the optical sensing apparatus 3200 furthercomprises a first planarization layer 3280 between the encapsulationlayer 3292 and the one or more lenses 3260, where the firstplanarization layer 3280 is composed of a third material (e.g., polymeror oxide material such as SixOy) having a third refractive index (e.g.,between 1 and 2 at the wavelength range absorbed by the absorptionregion of the one or more pixels 3240) that is within a threshold (e.g.,1%, 5%, or any other threshold that is tolerable by the system) from thesecond refractive index so as to minimize reflection when the opticalsignal L passes through the interface between the encapsulation layer3292 and the first planarization layer 3280. In some embodiments, thefirst planarization layer 3280 is configured to provide a substantiallyflat surface for the subsequent layer (e.g., encapsulation layer 3292,filter layer 3290 in FIG. 32B, second anti-reflection layer 3282 in FIG.32A, or one or more lenses 3260) to be formed on.

In some embodiments, the first planarization layer 3280 or the secondplanarization layer 3250 is composed of a material comprising polymerhaving a refractive index between 1 and 2. In some embodiments, theoptical sensing apparatus 3200 further comprises a secondanti-reflection layer 3282 between the first planarization layer 3280and the encapsulation layer 3292, where the second anti-reflection layer3282 is composed of a sixth material (e.g., polymer or oxide materialsuch as SixOy) having a sixth refractive index (between 1 and 2 at thewavelength range absorbed by the absorption region of the one or morepixels 3240) between the second refractive index of the encapsulationlayer and the third refractive index of the first planarization layer.In some embodiments, the sixth material of the second anti-reflectionlayer 3282 and the third material of the first planarization layer 3280can be the same. In some embodiments, the sixth refractive index iswithin a threshold (e.g., 1%, 5%, or any other threshold that istolerable by the system) from the second refractive index so as tominimize reflection when the optical signal L passes through theinterface between the encapsulation layer 3292 and the secondanti-reflection layer 3282.

In some embodiments, the optical sensing apparatus 3200 furthercomprises a filter layer (e.g., 3290 in FIG. 32C) between the one ormore lenses 3260 and the one or more pixels 3240, wherein the filterlayer is configured to pass optical signal having a specific wavelengthrange.

In some embodiments, the optical sensing apparatus 3200 furthercomprises comprising a second planarization layer 3250 (e.g., in FIG.32C) between the filter layer 3290 and the substrate 3230. In someembodiments, the optical sensing apparatus further comprises a carriersubstrate 3210 (e.g., the second substrate 2816 in FIG. 28) and anintegrated circuit layer 3220 (e.g., the first circuit 2818 in FIG. 28)between the one or more pixels 3240 and the carrier substrate 3210,wherein the integrated circuit layer 3220 comprises a control circuitconfigured to control the one or more pixels 3240.

In some embodiments, the substrate 3230 is composed of a materialcomprising silicon. In some embodiments, the absorption region iscomposed of a material comprising germanium. In some embodiments, theabsorption regions of the one or more pixels 3240 are at least partiallyembedded in a substrate 3230.

In some embodiments, the photo-detecting apparatus in the presentdisclosure further includes an optical element (not shown) over thepixel. In some embodiments, the photo-detecting apparatus in the presentdisclosure further includes multiple optical elements (not shown) overthe multiple pixels. The optical element converges an incoming opticalsignal to enter the absorbed region. In some embodiments, the opticalelements include lenses.

In some embodiments, p-type dopant includes a group-III element. In someembodiments, p-type dopant is boron. In some embodiments, n-type dopantincludes a group-V element. In some embodiments, n-type dopant isphosphorous

In the present disclosure, if not specifically mention, the absorptionregion is configured to absorb photons having a peak wavelength in aninvisible wavelength range equal to or greater than 800 nm, such as 850nm, 940 nm, 1050 nm, 1064 nm, 1310 nm, 1350 nm, or 1550 nm or anysuitable wavelength range. In some embodiments, the absorption regionreceives an optical signal and converts the optical signal intoelectrical signals. The absorption region can be in anu suitable shape,such as, but not limited to, cylinder, rectangular prism.

In the present disclosure, if not specifically mention, the absorptionregion has a thickness depending on the wavelength of photons to bedetected and the material of the absorption region. In some embodiments,when the absorption region includes germanium and is designed to absorbphotons having a wavelength equal to or greater than 800 nm, theabsorption region has a thickness equal to or greater than 0.1 μm. Insome embodiments, the absorption region includes germanium and isdesigned to absorb photons having a wavelength between 800 nm and 2000nm, the absorption region has a thickness between 0.1 μm and 2.5 μm. Insome embodiments, the absorption region has a thickness between 1 μm and2.5 μm for higher quantum efficiency. In some embodiments, theabsorption region may be grown using a blanket epitaxy, a selectiveepitaxy, or other applicable techniques.

In the present disclosure, if not specifically mention, the light shieldhas the optical window for defining the position of the absorbed regionin the absorption region. In other words, the optical window is forallowing the incident optical signal enter into the absorption regionand defining the absorbed region. In some embodiments, the light shieldis on a second surface of the substrate distant from the absorptionregion when an incident light enters the absorption region from thesecond surface of the substrate. In some embodiments, a shape of theoptical window can be ellipse, circle, rectangular, square, rhombus,octagon or any other suitable shape from a top view of the opticalwindow.

In the present disclosure, if not specifically mention, in a same pixel,the type of the carriers collected by the first doped region of one ofthe switches and the type of the carriers collected by the first dopedregion of the other switch are the same. For example, when thephoto-detecting apparatus is configured to collects electrons, when thefirst switch is switched on and the second switch is switched off, thefirst doped region in the first switch collects electrons of thephoto-carriers generated from the absorption region, and when the secondswitch is switched on and the first switch is switched off, the firstdoped region in the second switch also collects electrons of thephoto-carriers generated from the absorption region.

In the present disclosure, if not specifically mention, the firstelectrode, second electrode, readout electrode, and the controlelectrode include metals or alloys. For example, the first electrode,second electrode, readout electrode, and the control electrode includeAl, Cu, W, Ti, Ta—TaN—Cu stack or Ti—TiN—W stack.

In some embodiments, if not specifically mention, the cross-sectionalviews shown in the present disclosure may be a cross-sectional viewalong any possible cross-sectional line of a photo-detecting apparatusor a photo-detecting device.

As used herein and not otherwise defined, the terms “substantially” and“about” are used to describe and account for small variations. When usedin conjunction with an event or circumstance, the terms can encompassinstances in which the event or circumstance occurs precisely as well asinstances in which the event or circumstance occurs to a closeapproximation. For example, when used in conjunction with a numericalvalue, the terms can encompass a range of variation of less than orequal to ±10% of that numerical value, such as less than or equal to±5%, less than or equal to ±4%, less than or equal to ±3%, less than orequal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%,less than or equal to ±0.1%, or less than or equal to ±0.05%.

While the disclosure has been described by way of example and in termsof a preferred embodiment, it is to be understood that the disclosure isnot limited thereto. On the contrary, it is intended to cover variousmodifications and similar arrangements and procedures, and the scope ofthe appended claims therefore should be accorded the broadestinterpretation so as to encompass all such modifications and similararrangements and procedures.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the disclosure. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. An optical sensing apparatus, comprising: aphoto-detecting device comprising: a first substrate comprising silicon;a carrier conducting layer formed in the first substrate; an absorptionregion composed of germanium and in contact with the carrier conductinglayer, the absorption region configured to receive an optical signal andto generate photo-current in response to the optical signal, wherein theabsorption region is doped with a first dopant having a firstconductivity type and a first peak doping concentration, wherein thecarrier conducting layer is doped with a second dopant having a secondconductivity type and a second peak doping concentration, wherein thecarrier conducting layer is in contact with the absorption region toform at least one heterointerface, and wherein a ratio between the firstpeak doping concentration of the absorption region and the second peakdoping concentration of the carrier conducting layer is equal to orgreater than 10; and an electrode formed over the carrier conductinglayer, wherein the electrode is separated from the absorption region,and wherein the electrode is configured to collect a portion of thephoto-current.
 2. The optical sensing apparatus of claim 1, wherein thephoto-detecting device further comprises: a second substrate bonded tothe first substrate, wherein the second substrate comprises silicon; andfirst circuitry formed in the second substrate, wherein the firstcircuitry is configured to convert the photo-current and to an analogvoltage output for processing, and wherein the optical sensing apparatusfurther comprises a third substrate coupled to the photo-detectingdevice, the third substrate comprising second circuitry configured toprocess the analog voltage output to generate a digital output.
 3. Theoptical sensing apparatus of claim 2, wherein the absorption regioncomprises an array of pixels.
 4. The optical sensing apparatus of claim3, wherein the array of pixels are electrically coupled together togenerate the photo-current.
 5. The optical sensing apparatus of claim 3,further comprising a lens array configured to focus the optical signalto the array of pixels.
 6. The optical sensing apparatus of claim 2,wherein the first circuitry comprises a low-noise preamplifierconfigured to convert the photo-current and to a voltage output.
 7. Theoptical sensing apparatus of claim 6, wherein the first circuitryfurther comprises an amplifier configured to amplify the voltage output.8. The optical sensing apparatus of claim 7, wherein the secondcircuitry further comprises an analog-to-digital converter configured toconvert the amplified voltage output to a digital signal.
 9. The opticalsensing apparatus of claim 8, wherein the second circuitry furthercomprises a micro-controller configured to process the digital signal.10. The optical sensing apparatus of claim 6, wherein the firstcircuitry further comprises driver circuitry for a light emitter. 11.The optical sensing apparatus of claim 2, wherein the second substrateis bonded to the third substrate, wherein the second substrate isarranged between the first substrate and the third substrate, andwherein the first substrate is arranged to receive the optical signal.12. The optical sensing apparatus of claim 2, wherein the thirdsubstrate is wire-bonded to the first substrate or the second substrate.13. The optical sensing apparatus of claim 2, further comprising a lightemitter coupled to the third substrate.
 14. The optical sensingapparatus of claim 2, wherein one of more operating characteristics ofthe first circuitry is dependent on the absorption region, and whereinone of more operating characteristics of the second circuitry isindependent of the absorption region.
 15. The optical sensing apparatusof claim 2, wherein the digital output is used for proximity sensing,imaging, or time-of-flight sensing.
 16. The optical sensing apparatus ofclaim 1, wherein the absorption region comprises one or more pixels, andwherein the optical sensing apparatus further comprises: one or morelenses over a respective pixel of the one or more pixels, wherein theone or more lenses are composed of a first material having a firstrefractive index; and an encapsulation layer over the one or more lensesand composed of a second material having a second refractive indexbetween 1.3 to 1.8, wherein a difference between the first refractiveindex and the second refractive index is above an index threshold. 17.The optical sensing apparatus of claim 16, wherein the first refractiveindex of the one or more lenses is higher than 3, and wherein thedifference between the first refractive index and the second refractiveindex of the encapsulation layer is higher than 0.5.
 18. The opticalsensing apparatus of claim 17, further comprising a first planarizationlayer between the encapsulation layer and the one or more lenses,wherein the first planarization layer is composed of a third materialhaving a third refractive index that is within a threshold from thesecond refractive index.
 19. The optical sensing apparatus of claim 18,further comprising a first anti-reflection layer between the one or morelenses and the first planarization layer, wherein the firstanti-reflection layer is composed of a fourth material having a fourthrefractive index between the third refractive index of the firstplanarization layer and the first refractive index of the one or morelenses.
 20. The optical sensing apparatus of claim 18, furthercomprising a filter layer between the first planarization layer and theencapsulation layer, wherein the filter layer is configured to passoptical signal having a specific wavelength range.